How to resolve the Sync Error: You need to enable iCloud Drive (CloudKit is part of it)

NotePlan relies on CloudKit, which is activated when iCloud and iCloud Drive are activated, to sync your notes. For this purpose you need to be logged into your macOS or iOS device with your Apple ID and iCloud has to be enabled. If this is still not working, try:

• Check if NotePlan is listed in "Apps syncing with iCloud Drive" (find this in the system settings clicking on your profile picture on the left > iCloud > Drive).
• Disable, then enable NotePlan and reboot your Mac or iOS device.
• Uninstall NotePlan completely and re-install it again. Delete all folders associated with NotePlan (creating a backup first, which you can copy back later). Then reboot again if needed.
• Make sure you are using the latest macOS version.