Hi - I know that several folks are using Jamstix in Reaper and are raving about it. Interest tickled, I downloaded the Jamstix 3 demo. Issue is that in Reaper 64bit it won't load ("The following effect/plugin ould not be loaded") and in Reaper 32bit it just crashes Reaper. Maybe the difference has to do with my preferences, but issue remains that I can't use it.
Js3 works better in Reaper 4 than any previous version. My guess since your in the demo mode
ia possibly a acknowledgement pop up that is not visible at that time that needs to be acknowledge. It may be behind the add effect screen, or perhaps on the bottom window task bar. Most demo software pops an acknowledgment to select authorize or run in demo mode before the software will load as a vsti.
I demoed Jamstix 3 with Reaper 3.76. Going from memory the authorisation window to choose authorisation or demo was obscured. Unless demo was clicked I had the same issue. If you have clicked run in demo mode and this message from reaper pops up I would post it in the jamstix forum and the developer will sort it for you. Once you get it up and running it will take quite a bit of time to find your work flow, but once you do it's wonderful software.