Hi there! My name is ***** ***** I'd like to help you with your question.
Have you looked device settings for Express? I believe you can tick a box and it will automatically deleted successfully synced activities. It may think it was successful, so it isn't trying to reupload it. If that doesn't work, you might also want to power cycle the Garmin, remove the device from Garmin express, then once it powers back on, re-add it. One of those two things should do the trick.
If that solved your issue, awesome! I would greatly appreciate a rating of my answer. If you still need help, please let me know and I'll try to keep working with you. Thanks!
You are welcome. To make sure I'm understanding you correctly -
In the meantime I'll try to do some more research, I've not personally run into this issue, but I have seen a lot of people having sync issues, though not an exact match for yours.
Thanks for letting me know Dave. If you please rate my answer, I would greatly appreciate it. If you have any follow up questions, please do let me know. Thanks again!