AT and GA Modifiers When Billing CMT and Non-covered Codes to Medicare

Questions regarding using modifiers when billing CMT and non-covered codes to Medicare. We have used AT (Active) and GA (signed ABN) when billing active care for CMT codes 98940-98942 (e.g., 98941-ATGA) in the past. Currently we are told not to bill GA with AT. How do we bill?

GA and GY for Medicare Billing

We are using the ABN for non-covered services (such as therapy codes) when the patient is under active care. We are also using the ABN for CMT codes when the patient is under maintenance care. We are now confused about when to use the modifiers GA & GY when billing CMT & therapy codes. Would you please explain when & why each should be used for Active and Maintenance Care?