Thanks for the response Keri.
I've been having this issue literally all last week, and again all day today (based in the UK). In the end, I had to create a different account to try to get some to complete while still leaving the problem ones there in case you guys needed to check them out to troubleshoot (some did complete in the new account, BTW, some still haven't).
I've been waiting, basically, over a week for some reports which I eventually gave up on today (I needed them last Thursday and still have had no response back from the ticket I raised via Zendesk).
Is this a regular known problem at your end? It absolutely is at this end.