I deleted a run on the watch.
In Garmin connect web it is available, but I can't send it to the watch even if it is connected to a pc
In Garmin connect web it is available,
The watch is not designed to hold all of your activities and there is not a user friendly way to send it back to your watch, if that's really what you want…
Do you see what is queued in the devices menu? You should see a blue bubble with a number. If you click it you will see what is about to be synced.

I've actually never tried to send an activity to my…
You can try:
-export the original activity to your PC from GC
-rename the file to the original name (date-time.fit)
-simply copy it to the Activity folder of your watch
In Garmin connect web it is available,
The watch is not designed to hold all of your activities and there is not a user friendly way to send it back to your watch, if that's really what you want. If the run has successfully synced already with Garmin Connect, you should be good.
It's not so easy, because I don't want back the file of the warch.
I have edited the run on the web to shorten it.
So in my garmin account and on the app the run now is 5.0km instead 5.1km
On the watch I have delete the 5.1km run, syncronized it, but can't view the 5km one.
Do you see what is queued in the devices menu? You should see a blue bubble with a number. If you click it you will see what is about to be synced.

I've actually never tried to send an activity to my watch.
I synced several times with the Connect app but it didn't help. It was still in the queue.
When I connected the watch to Garmin Express is synced and the bubble disappeared in Garmin Connect, but I can't see the activity in the history on the watch so I don't know where it went...
Well, I don't need it on the watch. It is in Garmin Connect. I only did this to test the function and it didn't work that good.