I can’t download my realms word for limited storage even though I have free space.

I have been playing with my friends on a realm for a month now and I want to download a backup just in case. However I cannot do that now, it says I have limited storage and I can’t download it. I have checked my world which has roughly 600 MB and I have over 30 GB. I tried to sign in and out, nothing, checked help and couldn’t do anything useful. What can I do?

Please, I have to backup a realm and I desperately need a solution, Please.