O.K...
So through a bit of trial and error I've found the solution to my Indigo problem.
I first installed Digi's Distributed plug-in installers, which includes Indigo. This was my problem. The Indigo included in Digi's Distributed plug-in installers will not work with PT 6.4.1 (Even though this is the plug they include on the compatibility page.) This installer is Indigo v2.8 and will not work with PT 6.4.1 Mix!
So after downloading and installing several different versions of the Indigo (Indigo v2.8, v8.2 & v8.3) the only version I got to work on my old TDM Mix system 6.4.1cs4 is Indigo v8.2
I hope this info will benefit others and lead you back to why we are all here… Making inspiring music and not tech-ing out software revisions.
Best regard.
P.S. Super Mad Props to DutchMuzik… The 3000 Indigo patches are mind blowing..!
