Buttons on speedmaster 3612 callibre

I have the following speedmaster, which is five years old, and the seconds hands have stopped working. I am sure I fixed this issue before by clicking a combination of the buttons. But on checking ive found that the manual isays never click both buttons!! How can I fix this issue and does it need to go back to onega?

The only button which now works is reset and it's not resetting anything because the second-hand hasn't moved.

The warch serial number is 311.30.44.51.01.001.
Omega website link to my watch ... https://www.omegawatches.com/en-gb/watch-omega-speedmaster-anniversary-series-31130445101001