Had strange issue with PISDK on a machine due to versioning.
PISDK 1.3.6 was installed and the GAC showed OSISoft.PISDK.dll v22.214.171.124, when I looked at the assembly it was pointing to the right PISDK dll i.e. 1.3.6. Problem started that some tools like PI-SMT would not work and referencing the Interop assemblies from Visual Studio would be fine at design time but would fail to run, claiming it was expecting OSISoft.PISDK.dll v126.96.36.199 in the GAC.
Long story short, I traced the issue down to the bindingRedirect in OSISoft.PISDK.dll.config - if I removed the 188.8.131.52 -> 184.108.40.206 then everything starts working again (as that is what is in the GAC), even Visual Studio at run time. Now for some reason I normally get 220.127.116.11 in the GAC for PISDK, any ideas what would cause 18.104.22.168 to appear in the GAC? Want to make sure I am not missing something obvious.