Just tested and it works for me. Are you running any scripting blockers?
Also which one(s) do you want to be signed up for? If it fails I'll just insert you manually.
I'm not running a script blocker or anything like that. I tried again just now and the Farming signup worked but for Crafting I got a different error, saying that "We were unable to process your application for this competition because this RuneScape name is currently not ranked, therefore, it can't be entered." even though I definitely am ranked and just double checked to make sure I am.