None of the options to update my Apple Watch series 3 work what to do?

FWIW, a lot of people are having problems updating a series 3 due to lack of sufficient memory. Sometimes it takes 2 or 3 times unpairing/pairing the series 3 watch for the update to finally work. For possible solutions, see the reply to:

Problem updating Apple Watch Series 3 to … - Apple Community

WatchOS 7.4 can't be updated on Watch Ser… - Apple Community

Series 3 watch only has 4.8 of memory - Apple Community

or the replies to:

Can’t do update on watch - Apple Community

I have tried installing the latest update… - Apple Community

This is because the apple watch series 3 only have 8gb of space and the watchOS7.6 ask as minimium requierement 3.2ghz, after a hard reset you only have 2.4 as much so there is not much sense on the apple developers, i hope they resolve this problem on the next os.