Ceiling lights not working

HI have two ceiling lights (the circular pre- led ones) not working on my 2011 Worcester.  Some years ago I replaced one, but I have forgotten how to get started with removing the ring to access the light itself - any tips would be gratefully received, thanks

In my Symbol the frosted cover is held in by 3 lugs and you have to gently squeeze and the cover comes off.

Just a thought, I have a separate switch that controls all the ceiling lights and have found this to be a possible cause.

Regards Jeff

Finally got that sorted thanks - easy once you know!