Cat hasn't used the litter tray for about a month!

[SneakyGremlins]

I mean, wtf?

He only goes onto the roof (top floor flat) and is indoor otherwise. Where is he going? Is he shitting on the roof? or is he getting into another flat and using the litter tray there?

Probably both!! My cat hasn't used her tray in a few months but she goes outside. I think she uses next doors too! It's also possible he's found a way down from the roof to the ground and going somewhere outside.