Just to add to this - I've spent two days going through all this and getting stuck. Berkleigh and jer73's advice is all spot-on. I wish I'd found this thread earlier.
And just to be clear (because I'm not an IT expert), jer73 is saying clear the cache on your browser (Firefox in my case) not somewhere in the Diskstation virtual desktop.
Moderator: I've spent a total of four hours talking to your expert IT support and none of them could help me or knew anything about these simple steps. Could you please pass this stuff on.