I’ve had this ongoing issue…since Cubase 9.5 in which FX plugins randomly decide not to load or load. You can see the plugin but it is not highlighted in the mixer, hence will not work. The only way to even get rid of it is to use the new mixer undo (thank God!). These are legal plugins…and even the built-in Cubase 10 plugins will do this at time. One track will load the plugins, but another will not. It is always different in every project with no rhyme or reason why certain plugins choose to load or not load. I am going crazy with this and it is causing me lots of delays when composing. Anyone have any ideas what the hell is going on??? Thanks!
Hi,
I have never met this. Are you on Mac or Windows?
Could you try in Cubase Safe Start Mode, please?
Try trashing preferences.
Cubase is well known to get installed corrupted trashing preferences usually solves those issues.
What do you mean by “you can see the plugin, but it’s not highlighted”?
Thanks everyone! I will try all suggestions today. When I say it’s not highlighted, I mean that in the effects rack on the inserts you see the plugin there, but it is not highlighted, or colored, and hence cannot even be selected to turn it off. It’s like you turned the plugin off, but now can’t turn it back on. D’oh!
For the OP, yes I would either start in safe mode or trash preferences.
Martin, I have a few questions about this I have been wondering for a while.
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Considering the different options in safe mode, is one of those options identical as if you would have deleted everything inside the Cubase folder, meaning trashing preferences, then re-start Cubase to re-build?
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More importantly, if I was to do the trashing of preferences instead of using safe mode, I have always felt that before trashing preferences, I should first “hide” by re-naming any prior Cubase versions…for example if I wanted to trash C10.5 preferences, first re-name or “hide” C10. The reason for doing this is to assure myself that absolutely nothing is being carried over from C10 to C10.5 when I re-build or re-start C10.5. Am I being paranoid?
I think we both know the automatic transfer of key commands from one version to another doesn’t work. Therefore I always manually transfer those preferences.
Hi greggybud,
I have just explained the trashing preferences principle here.
The disable preferences option in the Safe Start Mode calls the factory preferences (even though the older preferences folders are still present). Cubase makes a backup folder if your original preferences. When you quit Cubase after the Safe Start Mode, Cubase deletes the temporary preferences and rename the backup preferences folder back to the original name.
There is a risk, if your preferences are actually corrupted in older Cubase version already. You use Safe Start Mode, it is fixed (thanks to the default preferences). Then you delete the current pretended folder and start Cubase. The issue is back, because the issue is copied over from an older corrupted version to the current one. (Did I describe it understandable?).
The preferences migration should work in general. And it always has worked at all if my systems. I haven’t been able to reproduce the not-migrated Key Commands bug.
I think so.
Then best practice would be to re-name any prior Cubase versions to avoid anything being copied over from an older corrupted version?
Hi,
Exactly. Actually not only one version. You should rename 2 or 3 older versions, because Cubase migrates 2 or 3 versions (I don’t remember now) back.
Btw, the renaming could be also tricky. If you rename “Cubase 10” folder to “Cubase 10_backup”, this wouldn’t work. Cubase takes the “Cubase 10” string as valid folder (for the migration only) and it will migrate the preferences to Cubase 10.5. You have to change the string at the beginning. So I asked rename the folder like “_currentDate_Cubase 10”. This works for sure.
Thank you!
I really feel this is important because a lot of users don’t do the above, or at least describe these steps before trashing preferences. I have learned the hard way. 
You quite certainly have “constrain delay compensation” activated. That´s intended behaviour then and no reason to KILL anything or to prematurely trash preferences.
HOLY CRAP!!! I actually have been using that recording my hardware synths…probably since I started having the problem. WOW!!! Maybe that’s it (not at Cubae right now to check). If that is it, I am dying of curiosity my certain plugins would load or not load due to that? …and some loading only on certain channels?
Well if the plugins latency are over the threshold.
Look it up in the manual, how to set the threshold, and what CDC really does.
Or just turn it off when you don’t need it 
Yes, that´s how CDC works, depending on where the channels you load them are in the monitoring chain. And not only depending on the threshold.
For OSX, I alway zip the pref folder and rename the zip file. Or just drag to desktop.