Housing element denied because of no gas safety certificate

Context: I am in a long-term sublet, approved by my flatmate's landlord/estate agent. My flatmate rents the 2 bed as a whole, and I pay her the rent for my room. I have a copy of her tenancy agreement for my own records, and we have a signed agreement between the two of us.

I paid her a deposit and my first month fine because of how assessment periods lined up. But my housing element has been denied because of all the evidence and documentation I was asked for, I haven't been able to provide gas and electricity safety certificates.

I know they are a legal requirement. But for the past nine days, our usually responsive property manager has not replied to any of my emails and has been unreachable by phone. I emphasised the urgency of the matter but no dice. They've always been so professional and thorough, so it is hard to believe they may not have these legally required certificates. I asked someone else in the building (they manage the whole building) and they don't recall seeing these certificates either.

I'm guessing it's because my agreement is unusual, but I have never been asked for these certificates in order for my housing benefit to be approved in the first place. Everything else the UC guy asked me for, I provided. My claim has been denied on the basis of the lack of these certificates.

I either have to move out or ask my flatmate to withhold the shortfall from next month's rent because this negatively affects her and it's literally because of them that she is £350 short (UC is continuing to pay me the same amount as they were previously, and my new place costs 350 more), not to mention the fact that it is illegal to not conduct safety checks. But she's not the one whose income relies on gas safety certificates, she's the one with an agreement with them, so she has no basis to withhold rent and wouldn't be protected.

I'm sure someone will tell me that's the reality of sublets - my agreement isn't with the landlord - but since when is a lack of gas safety certificates a reason for denying a housing claim?

Don't really know what I'm asking for here. I guess I'm just frustrated and need to get it off my chest. The London rental market is already bleak and having to deal with all of this is downright depressing.