Can't get reminders on my MacBook

If you upgraded Reminders, according to: Get ready for the new Reminders app

"Upgraded reminders aren't compatible with earlier versions of iOS and macOS. If you upgrade your reminders on your iPhone with iOS 13, your iPad and Mac using the same iCloud account can’t access your reminders until iPadOS and macOS 10.15 Catalina are available. Learn what to expect until all your devices have the latest software."

Catalina supposedly in a few days, but have you logged into icloud.com to see if they show there?

Great news & good luck. :)