Hey everyone - looking for help I’ve replaced the fuel cap and recently a sensor that was recommended by mechanic but today my fuel cap loose warning comes on. Any suggestions?

 

What codes are accompanying the light?
could be a faulty filler neck
Charcoal canister
Purge valve (s)
could simply be a vaccum leak at the hoses
Or wiring

 

So code is constant but has nothing to do with the cap unless it was a cheap cap( even cheap caps do a decent job)
The valve replaced means that you probably had a "large evap leak" and the mechanic changed the typical cap plus a visual check of a valve that showed possibly deterioration.
I see you are in Jersey which means rust. Quite possible you have a leak somewhere in your evaporation lines. Tell your mechanic he should smoke test the entire system to find that leak.