2000 Camry won't shift out of 1st gear

With the engine off see if the shift between 1st to 2nd feel,s free if not it could be the cable check the clutch is disengageing all the way it should go into reverse without crunching,other then that it could be a synchro ring worn check that the gearbox has the right oil in it.

try changing your gearbox oil

The problem is a gear internal failure the gear who drive the speed sensor is defect the is why you don't have speed sensor reading. There is a way you can verify that remove the speed sensor drive it with a drill check the dashboard you will see.

Yes you have to least have new gear synchronizers installed

To play it safe have the TPS checked out by another repair shop .If they say its ok then its the shift solenoids.

drain and fill trans with fresh fluid
trans may have to be rebuilt

sorry

you are experiencing early to mid stage transmission failure.

sounds like the governer gear stripped out , its located on the driver side on the trans where the axle inboard shaft goes into the trans

I would think its a transmission problem. have you tried shifting it manually. starting out in low or 1st gear then 2nd and then drive?