How to access drain in enclosed shower cabinet?

Hi, I want to access the shower drain but husband says that’s not possible as the drain cover Has not been fitted from above and the whole built in shower tray would have to be lifted which would be major, involving tile removal and much more. Any advice. We have tried all the usual things to cure musty smell and want to check it for build up of hair etc. It looks a pretty ordinary cover and I can post a photo if required. Thanks in advance.