3 bars can happen for a number of reasons. 34,000 miles isn't much though, what year is it? Been in storage a lot?
The start is almost always getting a scanner on it and seeing if it set any error codes and to check the battery voltage.
Have you tried the 3 bar relearn steps to get the car to relearn where the gears are?
The process has been documented a number of times, but the basic process is with the gear select in P, press the brake, turn the key on (without starting it), and it should start making little clunking sounds as the shift motors engage and disengage. If all goes well after the relearn the 3 bars should be replaced with P. Some people have luck moving the selector through the gears, but I have not found that necessary.
There are a lot of threads on the process to sift through, but it's a well known occurance that can happen for a variety of reasons and relatively simple to resolve if there isn't an unresolved underlying issue. That's where the OBD/canbus scanner comes in handy to figure out what the underlying cause was. Common causes are a tired battery, adjustment of clutch actuator, and worn out shift motors.
I would try the relearn process and if that doesn't help, you'll need access to a scanner (usually not terribly expensive).
My 2012 has recently gotten the three bars of death after sitting for a few months. I turned off the ignition, turned it back then, then moved the shifter through every gear. When I arrived back at Park the transmission began working again.
Make sure the battery is good and also attempt that re-learn procedure. In an absolute worst case scenario you may need to remove the clutch actuator (3 star bolts hold it on) clean and lube it, then replace it.
Well, the good news is, it WAS just the battery. MAN I panicked! After 12 1/2 years of only driving a smart and reading horror stories it was unexpected!! Strange thing is, my hubby's 2016 Rav4 battery was also dead that same day. He had it towed to the dealership and they ran tests and said it was just the battery, nothing else! THAT was a 2020 kind of day!