Apple Watch serial 3
I cannot update the last version to my Apple Watch serial 3
Apple Watch Series 3
Question marked as
The highest update possible for a Series 3 watch is 8.7.1.
Using your watch, open Settings, > General, > About to see what version it is currently running.
Then, if it's less than that, you should be able to see an available update for it by looking in the Watch app on the paired iPhone.