Claim rejection for ceiling replacement.

Good day I had an incident at my house on the 8th March 2021 my ceiling fell in on myself and in my dining room. I had an assessor come out the Wednesday 15th March 2021. I tried calling their office onwards from there and couldn't get hold of anybody to give me the outcome. I have been paying through my neck and have never claimed. Now only to hear that the assessor has written that the ceiling wasn't installed correct as the branding isn't to spec. This house was built 40 years ago and I wouldn't know anyway. No inspection from them at all when i joined as well. Now they rejecting my claim. I have moved to OUTsurance now but is still covered with them for March. I am shocked as i think they can see that I have cancelled my insurance as from 1st April and hence the rejection. This is ridiculous. I will never ever advise anybody to go there. How on earth would anybody know if the branding is spaced evenly behind your ceiling???