On the skyblock server, I am trying to complete the Rhyhorn challenge, but no matter what I do the progress bar never moves from 0
Yeah... we have been having issues with the new challenges system. This is a known issue that we are working towards fixing as soon as possible! Please just be patient!
I don't think you can do anything other than wait and hope for a fix soon. If you want, it's probably best to message a manager and ask if you can get past it somehow.