If you are using OpenCore Legacy Patcher it is possible that you are not being able to grant access permission to reminders and therefore you are facing a window saying "Access to Reminders is not enabled for Reminders MenuBar".
This issue is related to OpenCore Legacy Patcher as stated in the official documentation: OpenCore Legacy Patcher | Unable to grant special permissions to apps
A workaround is to use TCCPlus to add this permission. I would suggest looking up some threads on the subject and if possible making a backup before trying commands that might affect the use of macOS.
I cannot guarantee that TCCPlus still works or if it's reliable for new versions of macOS. The workaround below was tested by other users on issue #159, but if you decide to proceed it is at your own risk.
After downloading and extracting TCCPlus in the Downloads folder, open the Terminal and run the following commands:
cd ~/Downloads/
chmod +x tccplus
./tccplus add Reminders br.com.damascenorafael.reminders-menubar