Conway

I have a 2014 Sierra, never a problem till transmission went a month ago at 144411 miles. Shop had for three weeks got back the evening of 9-1-21,drove to work the next day no problem, went to leave work at 5 that afternoon does the same as yours. Turn the key and everything works try to start and dash goes black and click. Starts when it wants too. Had battery checked, was good, had starter checked it is good, spent Saturday changing cables and pulling all grounds I could find and cleaning them,put all back and started like a champ till today, no start no crank again, hope your shop can figure out