I've been unable to upload activities or courses to my Connect account, and get the error saying the file is already uploaded. I reached out to Garmin and here's their reply. Posted in case someone else is having the same issue. BTW, I'm located in the US. Can't explain the UK reply.

"Thank you for your enquiry.

This issue is something that we are aware of and are working hard towards a resolution, however, we do not have a timeframe for this to be completed as yet.

When the issue has been corrected, the fix will be released in a software update. This will be announced on your Garmin Connect account or on Garmin Express. If, at that point you require further assistance please contact us via our Contact Centre whereby we will be happy to talk you through it.

I’m sorry for the inconvenience.

Kind regards,

Chris

Garmin Europe"