The top range adjustment screw simply doesn’t move anything.
Is it possible I need a new front mech?
I doubt it’s broken, it’s just an incredible faff.
You’ll only notice any movement if the cable tension is tugging the derailleur against the limiter. If it’s not, it doesn’t matter how much you turn the screw, it’s not doing anything.
The way I got it working, I think, was to do it without cable tension and phsically push derailleur away from frame as far as it would go. Then turning the limit screw to make sure derailleur cog lines up over biggest ring.
After that, you can forget about limiter. Any further problems will be cable tension related.