I dont know where to start here
There is indeed a WinMX 2.6 (check the Archive Forested) and whilst its old it was designed for and is very popular with Opennap users, it does not feature the WPN system as we know it so I suspect SpiritWolf is not likely to be wanting the Community Patch.
This is an informative list of problems and solutions that apply to this older WinMX version SpiritWolf http://www.geocities.com/locojones2000/winmxfaq.html
Can I suggest section 16.1 as a starting point for resolving this error, I,m sorry we cant be more informative on the problems with this particular version but this forum was set up in 2005 and this client is from around 2001/2002 and thus we have no content history or posts to fall back on, however we will do our best to help you get reconnected
[Update] ERROR NEGOTIATING(217"15-INVALID REQUEST") Is this your exact error message, if so it may be that the file your trying to download is not at the location specified, another scenario is ISP blocking although that is pretty rare for OpenNap users in my experience.