Neptune Exotic 9.5kw water not heating up?

I have had the above shower for about 6 years and it has been working fine until this morning with the water only having a little warmth to it no matter how i adjust it.

When I had my shower yesterday there was a noticeable humming noise from the shower unit and it hasn't heated up since.

I have a combi boiler (Biasi) and this is working fine, hot water out of the taps and to the radiators are not a problem.

Will this be a heating element or something else?

Thank you in advance for any help!