I had the same problem and this thread helped me to find the logs and diagnose the issue but I suspect my case might be quite unique but I will post about it here in case anyone does have the same (or if PT want to fix it)
I run on a Mac as well as Windows via Parallels. I connect to the same Poker Tracker DB from both machines. This is not officially supported so the "bug" in my case is not really the fault of PT. I found the logs and I ran the actual SQL queries using a SQL client, I was able to find that I had 2 tournaments with identical tournament IDs but from different sites. This must have been because I had PT client open and running from both machines at the same time (I prefer to play on my Mac but iPoker is not supported there so I need to run this on Windows). I had always wondered if running 2 clients in parallel would cause issues so generally I try to avoid it but must have forgotten in this case, this has proven to me that it does cause issues.
The 2 tournaments were not significant so I just purged one of the duplicates and deleted the record from the tournement_results table and then my alias player worked!!
If you try this, you will need to known your way around postgres and you will of course know that you need to backup your DB before going in there! @PT Guys happy for you to take record of this and delete this post if you'd rather not have people poking around in the DB