Triton Trance on/off switch fell apart?

I have just bought a triton Trance to replace an opal that broke ( tried soldering the water flow switch but unfoturnatley that didn't work)

Fitting all went perfectly but when I went to test it the unit would not come on.

Having tested the supply with the cover off (not recommended I know) I switched the on/off mechanism inside on and the shower came on and seemed to be working fine for the 2 seconds i let it run for.

I then took off the platic tape on the front cover that covered the on off button to find two pieces come off with the tape - a rubber ring and the actual switch.

No matter which way round i try to put these back or strech it over the moulding it does not seem to stay together securely and nor does it want to actualy switch the switch inside on.

Any advice?