cooker hood filter

[Zappy50]

I need help. I need to change my cookerhood carbon filter but the cover is stuck. I moved here 4 years ago and havent changed it yet so i am guessing its greased stuck. I have been cleaning the grease filter but I didnt know there was a carbon one that should be changed every few months. I have tried WD40 but still won't budge.
It is a Lamona 2501 hood
Any ideas how to unstick it?
I would really appreciate help with this.

Don't worry, I doubt it's the grease.

Have you got a manual?

You can't usually just pull the cover off a hood/fan - there'll be a couple of catches somewhere that you need to press in to get it off.

If you haven't got a manual and can't find it online you could always tweet the manufacturer to ask.

Yes i downloaded the manual and it just says to twist the covers off

Oh I see

At the risk of saying something really stupid, you're definitely twisting it the right way? Sometimes if you're underneath something you don't.

That's probably not much help really, sorry.

I was going to suggest maybe using a toothbrush to work the wd40 into the crack but actually given carbon and fire risk is that a good idea, anyone know?

Sharp knife in the gap (be careful though)?