Similar issue here with my F2. I posted a message on this forum but have not seen an answer or a readable recommendation on what to do to correct the problem. :(
Since you are in the Garmin Connect forum I'll assume you desire to get your activity to the Garmin Connect website to view. If you are using the modern Garmin Connect website, then you need to have Garmin Express installed on you PC or macbook. If you did install Garmin Express and your activities are not showing up at the Garmin Connect website, then there is likely an issue with Garmin Express so you should be in the Garmin Express sub-forum. Look through the other posts that are similar to your issue or make a new post there.
There is also a Garmin Phone app that can upload activities from certain Garmin devices. If that is what your are using, then you should post in the Garmin Connect Mobile Application sub-forum.
Give some decent details of your issue, what software you are using, what you have already tried to resolve your issue and what Garmin device you have and even what type computer you use.
Posting about having an issue with little details makes many hesitant to want to answer, IMO.
I have similar issues with my vivofit. I deleted the device from the PC, and mobile devices after not getting data updated on the connect website or mobile app. Now after deleting the device I cannot connect again. This is the same on my PC, Phone and now tablet.
as suggested, have just posted a Q on the appropriate Garmin Express sub-forum, on potentially losing data while (over)writing data in GC when executing a forced upload, do you (Master) respond there as well?
No Junior Member, I seldom post in the Garmin Express forum as I don't use Garmin Express.
Note the "master" and "junior member" below the user names are just some assignment by the forum software. AFAIK, the only thing you have to do is make a lot of posts and you'll eventually be re-classed to something else. It's all silliness to me. Means nothing about whether any of my posts have ever helped or not, just that I post a lot.