Connectivity v2 causing error message "Oh no, it looks like you are offline"

[GuiltyRiceHusk]

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I have trouble accessing CS50's codespace, with the error message being "Oh no, it looks like you are offline", error details being "Error: Network Error".

A few days ago when I turned the Connectivity v2 feature off, I was able to access it. But now since it is enabled by default for all GitHub users and can't be disabled, it is showing this error message again.

My attempts to solve but in vain:

1. do not work on safari/firefox. The latter shows "Oh no, something went wrong!".
2. do not work with vpn, or without one, or with another vpn. (I'm in China so I have to use a vpn to access everything)
3. I did not turn on my firewall(I'm using mac).

This is how the 'console' in the Network tab of the Developer tools in the browser looks like.

CS50 has a troubleshooting for this specific situation but I am new in coding and don't really know how to check whether certain domains are blocked as it says.

I see my problem is pretty similar to #112351, but this one hasn't been solved yet. Please let me know if more information is needed to solve the problem. Thank you very much.

[slugsack]

Same thing happening for me. Tried different browser, different device, updating browser, turning off VPN, changing VPN location, clearing cache and cookies, restarting codespace, restarting computer, disabling enhanced tracking protections in Firefox, disabling my adblocker, and loading in desktop VSC. Only turning v2 off worked, when it was still an option.

The only success I've had beyond that is accessing the codespace via my phone's data, but with Canadian data rates, this is not viable longer term than about 5 minutes.

[GuiltyRiceHusk]

God, hope you find the solution soon... Sorry for the late reply, but please consider using another VPN! I did this a few days ago and it worked!

[slugsack]

Thank you for the idea - do you happen to use Mullvad, or another VPN with DNS blocking?

I had tried turning my VPN off already, but this time I tried closing the program entirely. The space then loaded fine. I dug around in the settings to see if there might be some setting that the VPN program uses even when "off", and I suspect it may be the DNS blocker for tracking. This might make sense given that VSC has telemetry and the blocklists Mullvad uses include a list for Microsoft tracking specifically. This doesn't explain why it worked when I was using mobile data, though. I still had my VPN on then.

This isn't an acceptable fix, in any case. If Connectivity V2 demands use of something Mullvad is blocking for privacy, that makes me uneasy.