I was just trouble shooting this problem for a few days, reading this thread and trying out the advice to no avail. I updated to the latest version of Logic the other day and still no luck. THEN I saw this error message more clearly! It said the component “Blackhole (” is not available! Not “Blackhole No Midi” or “Blackhole (No Midi)”. SO! I tried to rename the Blackhole No midi Component that I had moved out of the folder to the desktop to “Blackhole (“, put it back in that folder from where it came and lo and behold!!! IT WORKED!!! Old session now opens with the plugin!!! Not sure if I have an isolated case here, but figured it could definitely help someone out!!
(:
