A timesheet authoriser cannot access the system to sign timesheets - is there a problem with the site?

It is most likely due to settings or changes on their pc/network environment that is restricting their access to the site.  They should ensure they have our recommended web browser settings in place.

Please see the following Knowledge base articles: 

Internet Browser Security Settings

If the user is getting an invalid link then please see the following knowledge base article:

We have a timesheet that is Awaiting Authorisation but the authoriser states the link is no longer valid?