shifts in all gears except reverse on 2001 Chevrolet Suburban 1500

no warning, just did not work any more replaced module on transmission, no help.

these transmission are known to start to fail at approx 100k many miles do you have on the veh.
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1 more answer , 1 more comment
Reverse is controlled by the manual valve and not any of the electronics. If that gear is missing you have an internal component failure and you will need to see a transmission shop.
Not that I wanted to here but was what I thought also. Daughter had bought new part so I put it on
because parts store told her that was the problem, did not help. I thank you for your advice.