I'm asking if anyone can give me any ideas, a reconstruction of the 4l60E transmission was done, which the gears enter perfectly manually, but when we put automatic the 1st gear does not enter at any time, I directly have to accelerate more until it enters 2nd gear automatically. Could a sensor fail? Do I have to do anything else besides the physical change that was made to the transmission? thanks for everything.

Sorry for my bad english

 

Welcome to HF. We are going to need way more info than what you provided. There are many, many reasons your rebuild is not working correctly. We have no idea what you did, did not do. Any answer would be similar to pulling a random response from a hat.