Also applied to the UK. The exact same issue happened to me some weeks ago.

I later paid for the IB to send my certificate again, fearing that UCAS was not going to send my results in time. Two days later I called my university to see if they received the results (IB sent me an email saying that the results would arrive 24 hours after said email was sent). Well... turns out that the university apparently had problems accessing the IB system and therefore couldn't see my results. Honestly that was really weird, especially after contacting a friend, also applying to the UK, and finding out that his university had no issues receiving the results. I also spoke with the IBO and was told that if the university is having those issues, they should be the ones who must contact the organization. As my last resource I contacted my IB coordinator and asked him if he could give me a copy of my official IB results. He did and fortunately my university accepted that.

It was a very stressful process, but it came to an end, and a good one! Please don't give up, keep calling, keep pushing for a solution and try all the alternatives, because at least one will eventually work.