Helpdesk Forum stopped working

I have had the helpdesk (forum) extension with Contao 2.9.1 working on a beta site, where members could create topics and reply. I came back to the website a couple weeks later and found that members could not create or reply on the forum anymore, even though the icon links were there to click on. It just goes to a white screen with "page not found". Any suggestions?

Maybe at one point you have installed the "folderurl" extension.

In this case you need to edit the keyword list in folderurl and add all keywords of helpdesk (the parameter names appearing in the url)