unrecorded activity

Probably a corrupted activity FIT file. You can verify this by trying a manual upload to Garmin Connect Web - How Do I Manually Upload an Activity I Recorded to Garmin Connect?

If you get any message other than Import Complete, then there is a problem with the file. In that case, please attach it to this thread. We can take a look to see if it is repairable.

• Zip the file, then in a reply post Insert >> Image/video/file >> click Upload >> browse for file >> OK.
• Or upload the fit file to a reputable file sharing service, such as OneDrive, Google Drive, Dropbox, make the file public, then paste a link to the file in your post.

when I import a file, the website writes me a message that it does not support this file type

Then  - 

seilogramp said:

If you get any message other than Import Complete, then there is a problem with the file. In that case, please attach it to this thread. We can take a look to see if it is repairable.

2023-06-26-11-42-13.zip

how does one repair such a file ?

or  how can damage occur?

xsanchox said:

how does one repair such a file ?

I usually fix these using Fit File Repair Tool

Here's the repaired file - [solved]

Some suggestions to help minimize the occurrence of corrupt fit files:

• Sync your device then remove all activity fit files from your Garmin device using these directions - Removing Recorded Activities on a Garmin Fitness Device 
• Check for firmware updates using Garmin Express

HRM-Pro, Pro Plus, Tri, and Swim will sometimes corrupt activity fit files 

• Use the HRM download feature only after an activity where it was not possible to wear the watch
• Update the HRM firmware How Do I Update the HRM-Pro Software Using the Garmin Connect App?
• During the HRM-Pro download process keep the strap and watch in close proximity
• If issues persist even after the firmware update, contact Garmin Support
• More here about corrupted HR data: Corrupt FIT File Repair Requests

THX !!!

I'll ask if I understand it well (I don't speak English that well)

I uploaded the file via the web to connect. Now I have to synchronize ? Then delete all the files from the watch?

If you've uploaded the repaired fit file to Garmin Connect, then no need to synchronize. Then it is suggested to remove the fit files from the \GARMIN\ACTIVITY folder on your watch - support.garmin.com/.../