More then likely this is an issue with the valve body as a valve gets stuck and the fluid is just routed to that gear all the time.
You should have a manual valve where you can put the shifter in 1 or 2. Does first or second work when selecting the manually?
I would pull the valve body and and disassemble it to clean it and then retest.
I attached this process below. Let us know what questions you have. Thanks
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Tuesday, April 6th, 2021 AT 9:32 AM