I am having this same problem with Quickbooks 2020: I receive the error "Quickbooks couldn't save one or more schedules. Try again" each time I try to save a reminder schedule (SEE ATTACHED SCREENSHOT). I upgraded to this Quickbooks version in March specifically for the convenience of automated past due reminders, and now I can't send ANY reminders. At least my old Quickbooks had the capability to send reminders manually. I have contacted technical support and they sent me info on verifying and repairing my company file by rebuilding the database and also running the File Doctor utility. Both utilities report no problems. There appears to be an issue with this version of Quickbooks, but I am not willing to pay tech support any money to sort it out. You folks need to re-think how you treat loyal customers. Please pass our unhappiness on to your management.