Thank you for allowing me to assist you, my name is Joe and I will be happy to assist you with your concern today.
Check that the pioneer does not have an update available: https://www.pioneerelectronics.com/StaticFiles/PUSA/Car_Electronics/Firmware%20Update%20Files/Expanded%20Android%20Auto%20Compatibility/Firmware%20Update%20Instructions_AVH-4100NEX_FINAL.pdf
Depending on what android you have check if it is up to date as well. Not all devices are supported via bluetooth however via usb it should work but again not all devices are supported. Try resetting your android device and see if that resolves the problem for you.
I have had pioneer in my vehicles and always the flagship and I can tell you every single one it seems like one problem or another, their receivers drive me nuts, unfortunately for me while there were problems that were upsetting they still made the better out of the receivers.
Thank you!- Joe
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