Despite what you insist, it's not the same PC. Most-likely it's in the public vs home network configuration, which would have been reset on your fresh Windows install. But it's not like that's listed in the FAQ
As for "what else can be done", that FAQ post contains every known issue regarding connections with PMS. You may have found something new, in which case getting a packet trace (viewtopic.php?f=6&t=16005#p76239
) could help figure out what it is, but most-likely you've overlooked something listed in the FAQ.