Transmission not engaging when on a hill?

Hello,

This issue could be due to low transmission fluid.
When you have low fluid and past a certain angle the fluid might not reach the pump to allow the gear engagement.

https://www.2carpros.com/articles/automatic-transmission-problems

First check the fluid. Make sure it is at the correct level and in good condition.
Also, if the filter is clogged it can restrict the fluid flow thru the transmission which can also lead to issues.
If it has not been done, changing the fluid and filter is a good step.

I have attached the fluid change instructions for your reference.

Please let me know of any questions.
Thank you.