Unable to open Core Settings or Import characters on one game world

[ld-john]

Describe the bug
I have several games set up on one server instance, and one of the worlds has stopped being able to import characters from DND Beyond, and I cannot open the Core settings on that same instance.

To Reproduce
Steps to reproduce the behavior:

1. Attempting to reimport an already imported character, or a new character, results in an Error processing Character: TypeError: Failed to fetch
2. Attempting to open the Core setup window from the Configure Game Settings DDB-Importer selection results in nothing happening. In the Console a message appears suggesting that the request has been blocked by the CORS policy.

Expected behavior
Expect the character details to update from their DND Beyond Character Sheet or the Core setup window to open

Screenshots

Environment:

• Browser [e.g. chrome] Chrome
• Foundry Version [e.g. 10.288] 11.314
• 5e System Version [e.g 2.0.3] 2.3.1
• Module Version [e.g 3.1.21] 3.5.6
• Does this behaviour occur with other modules disabled: Yes/No (Find The Culprit module can help with this) I have disabled all other modules on the instance and reset to default settings and this has had no effect.

Additional context
Add any other context about the problem here.

• A Character URL, if the problem is a character import.
  This is one of the characters I have been trying to import. It will import when I add it to another game world on the same server - https://www.dndbeyond.com/characters/14814039

• Details of any errors in the browser console (press F12).

[MrPrimate]

Please try resetting here, as per FAQ for 2: https://github.com/MrPrimate/ddb-importer/blob/main/FAQ.md#my-core-settings-screen-wont-open

Although blocked by CORS error is normally related to something stopping your browser or app reaching the server - an ad blocker or antivirus, or firewall product.