If this issue was not there prior to servicing the unit then the likely issue is that it is still low on fluid.
This is common when changing the fluid that it either leaks and is low or was not filled completely after servicing. It will drive normally for a day or so but it may start having issues once the fluid is low enough that it starts to not engage.
I would suggest getting the engine and transmission hot and then checking the fluid again. Even if it is in the proper zone, try adding a quart so that it is slightly over full and see if it starts to engage better.
Please see the process below from the manual that will help with doing this.
Let us know what you find. Thanks
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Sunday, July 25th, 2021 AT 3:39 PM