Activity Map browser Extension not working properly for months.

Yes, this is a wide spread issues, see:

https://experienceleaguecommunities.adobe.com/t5/adobe-analytics-questions/activity-map-extension-is-not-working/m-p/624694

https://experienceleaguecommunities.adobe.com/t5/adobe-analytics-questions/activity-map-issue-chrome-extension/m-p/623627

This was posted by an Adobe employee as a workaround while Adobe attempts to fix the issue properly:

Just wanted to share a workaround while this being worked upon. It seems the recent release to Chrome have broken a functionality which was needed to run Activity Map.

 

The step below roll back this specific Storage Partitioning change that was introduced by Google and will allow Activity Map to work again.

 

Disable the new by-default Storage Partitioning feature:
reference https://developer.chrome.com/en/docs/privacy-sandbox/storage-partitioning/

Steps to disable -
Use Chrome Canary version 113 or higher.
Visit chrome://flags/#third-party-storage-partitioning
Disable the "Third-party Storage Partitioning" flag.

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And another user pointed out that this can be used for edge:

Works also for Edge, just visit edge://flags/#third-party-storage-partitioning

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Which isn't surprising since Edge is now basically a white labeled version of Chrome now (since the 2020 redesign based on Chromium)

I'm sure Firefox may have an equivalent if you are trying to use that browser, under the "about:config" area....