The lock out switch on my 2010 monarch doesn’t work.
It stopped working all by itself as it is my winter bike and I put it away for the summer.
If it gets fixed will it just break itself again?

I’d ask more “is it worth fixing a rear lockout”

I can’t recall the last time i used a lockout on the rear.

Sort of depends really. It’s going to cost £90 or so for a service anywhere which will be the starting point of a repair, plus bits so north of £100 easy.

You can buy newer, fresher, better shocks for that SH.