Adobe released Illustrator 2021 (v25.1) on 6 January. It initially broke backward compatibility for third party plugins for macOS users. This has now been addressed with the Astute Graphics updates issued on 13 January. Please use the Astute Manager to update your plugins to ensure compatibility.
For information on how to update your plugins, please refer to Discovering and installing plugin updates.
Special note for Grandfathered accounts
If you purchased an Annual Service Plan which expired (ie. was not renewed) prior to the updated Astute Graphics plugins being released on 13 January 2021, your plugins will not become compatible with Illustrator 2021 (v25.1) on macOS until you resubscribe. You can easily do this by logging back into your Astute Graphics account.
Alternatively, you can remain with Illustrator 2021 (v25.0.1). If you have already updated Illustrator manually, or it was automatically updated for you, you can follow these two simple steps in the Adobe Creative Cloud manager to revert: