Hello, everybody!!!
I'm reviving this post because I stumbled across the same issue. Massive was working fine as plugin until last week...
Now, i can only open it in standalone mode. This means it is installed correctly. Component, VST 2, VST 3 all in place. NI Access updated it to version 1.5.9, which i think is the last compatible with Logic Pro 9 that I'm using. Do you think that updating might be the problem?
Any help is appreciated!!!
Thank you,
Dimitris