Cannot add tasks anymore

Suddenly I'm unable to add a task, as of this afternoon. When I try to, it appears blurry on the week view and eventually a little hazard symbols appears next to it. When I refresh the page what I've added is gone. Something is definitely wrong on the site end as the same occurs after refreshing the page, logging in and logging out, trying on a different device, etc. The site otherwise appears to be functioning normally and all my existing tasks can be viewed.

I depend on this app to keep my work organised, and it suddenly not working is very stressful, and disappointing considering how expensive the yearly fee is. Please fix ASAP!