Cannot create FBA shipments

I cannot create FBA shipments on Amazon and cannot work out why. I am UK seller trying to send to UK Fulfilment center. The normal preferred carrier UPS is not available, I get an error and cannot select a non-amazon partner carrier either so I am stuck. This is happening with all of my ASIN's, I am getting nowhere with my case I have logged with seller support, spoken twice now to them and get unhelpful replies - I last sent a shipment on the 1st of June so all was fine, I have previously sent this ASIN in before multiple times, there is no issue with the dimensions or weight, the packing template is fine) I need some advice on how to escalate please people as I have products that are selling well to send along with new products- thanks in advance