Front and door speakers stopped working, all at same time.

Try another loudspeaker across a rear speaker to check if it is a wiring issue first.
Is the fader control set correctly I wonder.

fade setting?

Check to see if your speaker wires are cut from the radio to the speakers. Not all of the speakers will stop working at the same time. On my 2001 expedition, the front worked but not the doors or rear. I found a cut speaker wire that is located behind the windshield trim above the stearing wheel where someone had installed an air freshener with a screw

There is no fuse to the speakers your rear speaker wires should run under the kick plateon drivers side broken or disconnected wire or burned out channel in radio.

Could have damaged the speakers or the radio or both.
You could pull a door panel and connect a small used speaker to see if the radio is producing a feed to the door.

1997 Chevrolet Tahoe Car Radio Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: Brown
Car Audio Front Speakers Location: Doors
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: 6 1/2? Speakers
Car Audio Rear Speakers Location: Rear Doors
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

take one of the front speakers out and pull out the head unit and unplug a set of audio wires(front right, front left ect.) and hook it up directly from the radio to the speaker there for bypassing all the cars wires. If it works then there's a problem with the car's wiring(maybe an inline amp). If it doesn't work, then try a known good speaker from somewhere else(home stereo speaker for example) and connect it to the radio, if the speaker works, your radio is fine and there may be a problem with the speakers. If it doesn't work then you have a problem with the head unit.

With the lack of information provided all I can suggest is ..
1. are the speaker wires connected at the radio? 2. are there rear speakers and if so do they work? 3. make sure the fader control isn't set to rear, this would shut your front speakers off

Constant 12V+ Green/Purple

Switched 12V+ Yellow/Black

Ground Black/Light Green

Illumination Light Blue/Red

Dimmer n/a

Amplifier Remote Blue

Antenna Right Front

Front Speakers 5" x 7" Doors

Left Front (+) Orange/Light Green

Left Front (-) Light Blue/White

Right Front (+) White/Light Green

Right Front (-) Dark Green/Orange

Rear Speakers 5" x 7" Rear Doors

Left Rear (+) Gray/Light Blue

Left Rear (-) Tan/Yellow

Right Rear (+) Orange/Red

Right Rear (-) Brown/Pink

best wishes

check wiring on passengers side near the rear hatch speaker, the rear door speakers are run through them also. i had the same problem and it was a unplugged connector at that location