There is currently a bug which affects validation only when running Logic Pro natively on M1 (outside of Rosetta 2).
Here's the workaround:
- Run Logic Pro with Rosetta enabled (right click Logic Pro > Get Info > tick ‘Open using Rosetta’).
- Re-validate Channel Strip 2 in Logic Pro’s plug-in manager.
At this point you may keep Rosetta mode enabled or turn it off.
Repeat the steps above if the plug-in should ever become invalidated again.