Sorry

This reference is invalid, unknown or expired

This may happen for several reasons, the main reasons being:
The request has been closed
The originator of any request has a "close" button and may have used it. Please see with them if that is the case
The link does not exist
For example from a copy & paste and the last character is missing
The link has expired
Nothing you can do there, though you may complain to the original request creator
N.b.: all files have been removed
Wrong user
You are trying to access a request you created as a functional account while being yourself, or the other way around
Switch to the functional account, or back to yourself, and try the link one more time
I blame the firewall
Good luck