Delaying withdrawal for nearly 2 weeks

I made withdrawals totalling around £13,500 on the 27th March my account was fully verified and all my documents were accepted months ago, so there was no issues with verification. They still haven't paid out and were claiming they needed to check the account but can't give a timeframe and are not replying to any emails. Every time I try and get a update I get the same reply that the relevant team will reach out it's up to two weeks and nobody is reaching out. I've been told they are verifying my account which makes no sense as i'm fully verified, then im being told they are doing checks as its a large win. They are stalling the payment for a unknown reason and won't communicate at all. They closed my account but said they still need to carry checks which makes no sense I just want them to process the withdrawal asap. I didnt get a notification that you have requested evidence I can send that now.