I bought a Adafruit branded TCA9548A I2C mux as well as some generic TCA9548A development boards from Amazon (In fact they look just like what is pictured on this video:
I have the adafruit one working just fine with an Arduino Pro Micro and three128x32 I2C OLEDs on attached to the mux. I have pull up resistors for the signal lines on the OLEDs and it all works great. In fact my schematic is exactly as shown in the above video.
If I substitute the "generic" mux dev boardthe screens never light up. I can see the mux address with the I2Cscanner, it is at least partially working
Has anybody else come across anything similar to this?