I just went thru the exact same thing with my 2018 F150. Batteries charged, motor just clicks when trying to start or try to tilt motor and battery voltage measured at the pos cable on the starter drops to 3 to 4 volts. Long story short after spending 5 or 6 hours of troubleshooting over several days I was about to post my problem here. I knew it was a "simple" 12v problem but I was stumped. I even pulled on all of the battery cables, they were all tight. After reading many posts here that guys say "disconnect each cable and clean the lugs until shiny" I decided to bypass the battery switches and positive cable with a jumper cable and go from the pos battery terminal to the starter, no change. I then bypassed the negative cable and connected the battery neg directly to the chassis of the motor and guess what, the trim worked and I was able to start the motor. Even though I pulled and twisted all battery cables I tightened each nut on the batteries 3 out of 4 were tight and didn't move but the one neg cable lug nut tightened no more than a fraction of a millimeter it was loose enough causing the 12 volts at the starter to drop to 3 or 4 volts while trying to start or use the t&t. I'm happy I was able to fix the problem but I don't know if I should feel bad that it took me so long to figure it out. I added an extra nut to each terminal.
