"Something went wrong. Please, try again" On Sign up. Communication between frontend and API Docker containers

[TheCass1]

Hi.
I installed Myfin with docker and its three containers are created and started (DB, API and Frontend).
The frontend is reachable, but when I try to create a new account by clicking the "Sign up" button and entering all the infos, the page return "Something went wrong. Please, try again". I've read from past issues that it could be a communication problem between the frontend container and the API one.
The API container is exposed with https (port 443) to the internet by a reverse proxy pointing to localhost:3001. I confirm that it is reachable from the outside.
I've correctly set the "VITE_MYFIN_BASE_API_URL" env variable in the docker-compose.yml file with the API url "https://subdomain.domain.com" but the UI doesn't allow to create a user.
If it could help, I've also tried with the Android app setting the "API Base URL" as the same of the VITE_MYFIN_BASE_API_URL variable, and it returned "HTTP 401" (maybe because any user has been created yet), so I think the API server is correctly reachable.
Thanks in advance <3

[afaneca]

Hi @TheCass1,
This seems indeed to be an issue of communication between the frontend and the API. If the connection had been established successfully, you would have been redirected to the onboarding flow (where you are asked to create your initial user and set some default settings/preferences).

Could you inspect the network tab of your browser and let me know what XHR calls are being made and to what API address?

That should allows us to better understand what the issue is.

[bmp152]

Hello. I seem to be having the same issue as @TheCass1 . I am launching the frontend, api, and database with docker compose and can confirm that they all run correctly. I also have the frontend and api exposed via an nginx reverse proxy and receive the expected "{"info":"MyFin API","version":"3.5.0"}" when visiting https://api.mydomain.com. The main frontend page is also accessible at https://www.mydomain.com but get stuck at the login without it proceeding through initial account setup. My "VITE_MYFIN_BASE_API_URL" in docker_compose is set to "https://api.mydomain.com". I also have port 3001 open on my firewall but that doesn't seem to change behavior whether enabled or not. SSL certificates are issued from letsencrypt for mydomain, www.mydomain.com, and api.mydomain.com. DNS A records are also set for each.

I did poke around the Network tab in Chrome and see that there are two xhr errors throwing 500 codes. I'm happy to provide more information if helpful. Thanks in advance! Errors are as follows:

Request URL
https://api.mydomain.com/validity?t=1768167787730
Request Method
POST
Status Code
500 Internal Server Error
Remote Address
107.173.redacted.redacted:443 <---my external IP
Referrer Policy
strict-origin-when-cross-origin

Response Header:

HTTP/1.1 500 Internal Server Error
Server: nginx/1.24.0 (Ubuntu)
Date: Sun, 11 Jan 2026 21:43:08 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 64
Connection: keep-alive
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 96
X-RateLimit-Reset: 1768167808
Access-Control-Allow-Origin: *
Content-Security-Policy: default-src 'self';base-uri 'self';font-src 'self' https: data:;form-action 'self';frame-ancestors 'self';img-src 'self' data:;object-src 'none';script-src 'self';script-src-attr 'none';style-src 'self' https: 'unsafe-inline';upgrade-insecure-requests
Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Resource-Policy: same-origin
Origin-Agent-Cluster: ?1
Referrer-Policy: no-referrer
Strict-Transport-Security: max-age=31536000; includeSubDomains
X-Content-Type-Options: nosniff
X-DNS-Prefetch-Control: off
X-Download-Options: noopen
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-XSS-Protection: 0
Content-Language: en
Set-Cookie: i18next=en; Path=/; Expires=Mon, 11 Jan 2027 21:43:08 GMT; SameSite=Strict
Api-Version: 3.5.0
Access-Control-Expose-Headers: Api-Version
ETag: W/"40-J6Nb4wdi00qF28S6F2Qtk+l6248"

Request Header:

POST /validity?t=1768167787730 HTTP/1.1
Accept: application/json
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: en
Cache-Control: no-cache
Connection: keep-alive
Content-Length: 0
Expires: 0
Host: api.mydomain.com
Origin: https://www.mydomain.com
Pragma: no-cache
Referer: https://www.mydomain.com/
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-site
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36
authusername: undefined
sec-ch-ua: "Google Chrome";v="143", "Chromium";v="143", "Not A(Brand";v="24"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "macOS"
sessionkey: undefined

The second 500 error is basically identical with a different t= parameter passed (https://api.mydomain.com/validity?t=1768167788033).

[afaneca]

Hi @bmp152,
When MyFin is running for the first time (with no users registered yet), the /validity endpoint should return a 404 error, which signals to the frontend that it needs to redirect you to the initial setup page. However, you're getting a 500 Internal Server Error instead, which suggests something is failing before that check can complete, most likely a database connectivity issue.

Could you share the output of the API container logs?

This should help us pinpoint exactly what's going wrong. Look out for any database connection errors or stack traces around the time you see those 500 errors in the browser.

Thanks!

[bmp152]

@afaneca
Thanks so much for your reply. I spent so much time troubleshooting, thinking it was something wrong with SSL security or proxying. After looking at the docker logs for the myfin-api container as you suggested, there was no activity other than the db and api services starting and listening.

It turns out that when I changed the MYSQL_ROOT_PASSWORD in the docker-compose file, it contained a special character ('@'), which apparently was breaking communication. I issued "docker compose down -v" and edited the password to remove any special characters and voila!, it worked perfectly. I was able to step through a new user setup seamlessly. Also, after inspecting the logs for myfin-api, I was able to see a series of prisma/migration actions.

Thanks so much for your response! I'd be happy to share an installation guide and/or my nginx reverse proxy configuration should it help others.

[afaneca]

voila!, it worked perfectly

That's great to hear! Hope MyFin can be useful to you :)

I'd be happy to share an installation guide and/or my nginx reverse proxy configuration should it help others

If you do create something (whether it's an installation guide, your nginx setup, or troubleshooting tips), just let me know and I'll gladly link to it from the official docs.

Thanks