The slipping and no engagement at this point sounds like a pressure issue inside the transmission. You have a pump in the transmission that maintains the proper amount of pressure needed to apply the clutches that engage each gear. I attached the system information about this system for your review.
Let's start with checking for codes because this could just be a bypass valve issue but if the fluid is full then I suspect it is an internal issue. If you can, let's check the line pressure of the unit and we can confirm proper pressure. I attached the spec for line pressure and the test port location.
Here are a couple guides that will help with getting codes and if you don't have a scan tool then just stop by a parts store (if possible) that does this, and they can scan for codes free of charge.
https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing
https://www.2carpros.com/articles/automatic-transmission-problems
Let me know what they are and we can go from there.
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Saturday, April 18th, 2020 AT 8:37 AM