Gainsborough Energy 2000X electric shower ?

I hope you can help me fix my problem. Basically I was checking a new
shower head and it must have had an 'OFF' position. So this caused the
Pressure Relief Valve to blow off. I took the front off the shower and
a small metal bracket fell on to the floor. I then re-inserted the PRD
and tried to find a place to refit the small metal bracket. I made many
attempts without success. So each time I switched on the shower the PRD
blew off again. My shower is a Gainsborough Energy 2000x and the PRD in
question is Gainsborough Pressure Relief Device 9.5kw 95607524 as shown
on the 'THE SHOWERDOCTOR' WEBSITE.