EC Claim denied

I apologise if this is the wrong forum,

I have contracted COVID a week before I had an assignment due and because I also have CFS/ME I knew I was going to get very ill and need an extension on my assignment. I asked for 14 days extension and my claim was denied due to insufficient evidence but my university know about my disability, I explained my situation and showed covid tests and I also have a support plan that is supposed to make it easier for me get an EC claim. They told me provide more evidence within 14 days to get a review but the deadline is in now three days ( it was never more than a week away ) and I can barely look at my phone, let alone fight them to find out what they consider “good evidence” because they didn’t even tell me or tell me how to find out. Additionally, the uni closed for the holidays on Friday so now my emails for help are going unanswered. In these emails I am again explaining my situation but nobody is going to be back on campus for a month now.

I want to file a complaint of some sorts (or at least raise an issue) because I’m supposed to be supported through my disability in my studies but instead of recovering from COVID, which could make me sicker forever, I am being forced to finish a decently big assignment through vomiting and tears. (sorry I know it’s ew) My question is:

Can I legitimately take issue with their decision? It feels unfair but is it actually worth a complaint of some kind?

I’m a good student, I care a lot about my grade and I can’t really stomach submitting an assignment late with no support measures in place to give me leniency, so now I feel I’m being forced into a corner of working despite being so ill that this post feels like my best work this whole illness. Would love some advice so that at least in future I might have an easier time