I've had Nebula 1.3.811 working happily in Cubase 7.5.30 (win7 64) for months.
Today, I open one of my sessions (which was working perfectly yesterday), and I get the Cubase message "The plugin Nebula Reverb cannot be found for channel etc."
- However, the plugin is clearly there! It's in the Plugin Information list, and I can also add a new instance of it fine. (there's actually two entries in the plugin list, one for the actual Nebula plugin, the other for the 'missing' plugin).
Seems to be an issue in Cubase. Please try this trick.
Find a heavy CPU consumption plug-in in the problematic session and rename it as: example.dll to example.old. Load again the problematic session and the renamed plug-in will not be loaded into the session due Cubase will be not able to find the dll file. This trick will bring some extra CPU to load Nebula.
If you still have problem with your session, submit a support ticket.
yes Nebula is authorized, I can open a new instance no problem, and also save the session and load it fine. It's just loading existing sessions where it doesn't find it.
I had a quick peek in the cubase session file with a hex editor, and found references to '4629' near to Nebula instance settings, which is the correct plugin ID / magic number specified in the config XML file.
I'm in contact with Steinberg about it, will let you know what they come up with.
One thing that did happen -- Cubase's preferences became corrupted, and reset (this happens with Cubase occasionally, and is a known issue). This is when the problem started. I've tried 'trashing' the preferences since, but it doesn't help...