No hot water from Aqua Lisa Shower

[pmp4]

I wonder if anyone can shed some light on this problem.

I have an Aqua Lisa shower. I am not sure what model it is but is integrated into the wall with just the round mixer tap coming out of the wall.

The problem is that there is no hot water coming from the shower but still hot water going upstairs to the bath and sin taps.

What would cause this?

do I have to replace the cartridge?

 

[muggles]

Either a broken cartridge or a blocked filter, the filter is in the back of the cartridge so you'll have to take the cartridge out either way

 

[pmp4]

Thanks ever so much for the advice. Will I need to turn the water off?