If you are running Reason 12.6 natively on an Apple Silicon (M1/M2) computer, you need to update all your additional/external Rack Extensions so they also run natively on Apple Silicon.
If you are running Reason 12.6 as part of a Reason+ subscription, click the Devices tab in the Reason+ Companion app and click "Upgrade all installed devices":
If there is no "Upgrade all installed devices" item on the Devices tab, make sure you're running the latest version of the Reason+ Companion app.
Select "Check for updates" on the Help menu in Companion and update if there is a newer version available:
Also make sure you have installed the latest versions of your Rack Extensions!
If you are running a perpetual (licensed) version of Reason 12.6 on your Apple Silicon Mac, upgrade your Rack Extensions here instead - via Authorizer (Rack Extension Manager).