Minnesota

command-shift-delete keys pressed at the same time, then released. Clear everything. This will wipe out any log-ins, but should clear out anything set by mistake. it might also be due to needing an update to Firefox (check help, about to see if there's an update).

THat site could be switching to paid mode and your ad blocker could be interfereing. It could also be a very old computer running a no longer supported macOS version.

There are a few things to try. But unless you have a techie friend sitting at your keyboard trying things out, it will be tought to help too much more from the other side of the country