I have a SG90 type servo (blue plastic, probably clone, got in kit) that works perfectly with Pi Pico and ESP32 both with Micropython and Arduino. I bought 12 of the MG90S servos (probably also clones) but I can't get any of them working in the same circuits with the same code. is there something code wise or in the circuit that needs to be changed to get them working, or am I just SOL? Thanks in advance, I hope I put this in the right forum.
The MG90S servos should work as the others do.
As always, the 3 pins need to be connected properly.
How are you powering these ?
I'm powering the ESP32 (my current setup, but the same for all) with USB, the servo with 9v battery through 5v regulater, with common ground for servo and ESP. Running signal thru pin 2 on ESP to verify code is working via built in led. SG90 works perfect with this setup, but MG90S not a whimper. Wire colors are brown (gnd), orange (vcc) and yellow (signal). both servos have identical connectors with colors all wired the same.
Such a battery can not drive strong servo motors. Also the regulator will shut down the output on overload.
I'll try a power brick tomorrow, will post results... Thanks 
Like others said, it's not good to power servos with a 9V battery. BUT, it should deliver enough amps to power at least 1 of these small servos. So if your setup worked with (1) SG90, I see no reason why it shouldn't work with 1 MG90. I checked specs of both, they are pretty much the same. The main difference seems to be metal gears (MG) instead of plastic gears (SG).
Strange.
I couldn't find the power brick... I switched power supply to 2 unregulated AA batteries (3.3V), same results. I measure 0.1 V drop on the SG90 when operating, no fluctuation on the MG90. So far I've only tried 3 of the MG90s, will go ahead and try the other 9... I'm kind of out of ideas 
What's the voltage rating of the servo? There's more than just a motor in those, there's an integrated circuit; if it won't work reliably at 3.3V(the best two AA will give you), then you've just tested something that shouldn't work.
Is DMM synonym of DVM?
Digital MultiMeter... 
@bullwood when your servos are at stationary, will they need to still supply supporting torque.
If so when they have stopped where you command them to go, they will still be consuming current to keep their position.
Tom.. 
There is no voltage drop, the MG90s are not drawing any current. When rying to run with 9v battery, there was no voltage drop with the MG90s. The SG90 works perfect with both setups. I tested 12 of the MG90s, all with same negative results. I did take one of the MG90s apart, it was plastic gears with no bushings or bearings, definately a very cheap knockoff... hey, they were cheap, you get what you pay for. I'll try again in about a week when my new goodies come in, but I don't have much hope.
The MG stands for Metal Gears. They were probably fake devices never intended to work
Since you've opened one, check to see if they're miswired, before you toss them.
Hi, @bullwood
Have you tried the servos on a 5V controller, like a UNO or Nano with a simple sweep program?
Tom..
I'll have 3 amp adjustable voltage regulated bench supply in a few days ... Also have a robot dog kit coming that I can swap and test... I'll post results, and thank you everyone here for your suggestions.
Just tried with a 2 amp power supply, the MG90s are totally dead... no voltage drop, no movement.
Tom: I don't have a UNO or Nano at this time. I will try your suggestion when I get one.