Reminders with nothing shown

When something like this occurs it is always worth going back to first principles. Please check on each device you wish to synchronise reminders between that they are set to be using iCloud to share reminders with each other and are using the same Apple Id, or the reminders list is shared with another Apple ID. (those two mechanisms differ)

It may be helpful to log in to iCloud.com to see if the Reminders are populated there as well.

Did you double check the first paragraph of the things I suggested to you?

If all of those are correct then it is worth booting into Safe Mode, which has a way of cleaning out files that gett into the way of correct functioning