Wont shift into overdrive?

Hello,

What is the engine RPM that you see at 60 MPH?
Driving on a leveled highway (no up or down hill) at a steady speed, you should see around 2000 RPM.

If is it is significantly higher than the transmission might not be selecting the overdrive.
If it is not shifting to overdrive, first this needs to be checked is the fluid level and condition. As low fluid can prevent the transmission from shifting, also having contaminated fluid can trigger similar issue.

Another possibility is a faulty transmission pump. When the transmission does not have adequate fluid pressure inside it can have shifting issues.

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

Is the check engine light illuminated? Many times with transmission issues the engine light comes on.

Please let me know of any questions.
Thank you.