That link works for me also. here is a copy of mine -
https://worker.mturk.com/?filters[search_term]=pandacrazy=on - I do get a "flash" of the new worker site, but it loads PC in a second or two. I run my PC in a separate window not tab. Some on earlier said they had to restart their computer to make the same problem go away. Maybe try deleting PC and helper from your script manager, log all the way out, close everything, log back in, reinstall PC and PC Helper from here -
https://greasyfork.org/en/users/6406-johnnyrs.
Wish I could help more.