[General Questions and Answers] TheDoctor549:
Hey, everyone. This is my first time on this site. I don't have a lot of experience with android as I am more of an iphone guy. I'm the manager of a small doctor's office here in south Texas and, until recently, we've been using the PAX A920 to take payments on. Doc said he didn't want the devices anymore and that I could have them to play around with. I'd like to completely wipe the devices and install just a straight android OS on it. But I have tried literally everything I can think of. I'll list a few things about the device, everything I have tried, and a few pictures below. Any help would be greatly appreciated.

Device specs and things I've tried:

When I plug the device into my computer (OS X Monterey) and open the Android File Transfer tool, I can see a little bit of stuff that is on the device, and a notification pops up on the PAX that says "USB debugging connected. Touch to disable USB debugging"

I can drag and drop APK's to the device but none will successfully installDeveloper Options cannot be accessed. When I try to tap the build number, a message displays at the bottom of the screen that says "You are not debugging and have no access to developer mode !" In exactly that format. I've also tried to enable developer mode with ADB using "adb shell settings put global development_settings_enabled 1" but that didn't work either.

When I turn off the device and power it back on, while holding the power button and volume up button, it displays the PAX boot logo but it says "Firmware Developer Mode" underneath it. It does nothing else from that point. I tried letting it sit for like 6 hours and nothing ever happened.

It appears that PAX devices use their own custom android based OS called Paydroid and I can't find anything about it after some pretty extensive google searches.

The build number is PayDroid_5.1.1_Aquarius_V02.3.17_20181026

The Kernel version is 3.10.49

It's running on Lollipop

Underneath processor, it says "Qualcomm Technologies, Inc MSM8909

The device has it's own store called PAXStore but it's pretty useless

You can't browse the internet on it

There's a whole bunch of crazy looking applications loaded on the device but you can't access any of them.

ADB recognizes the device but almost any command I use that targets the device literally does nothing. No success message when using "adb install" and no output with "adb shell getprop" or adb wm size". Zero. Zilch. Nada. The only one that actually gave me some form of output was the "adb pull /system/build.prop" and that one was "adb F 01-20 10:43:25 72984 1577471 file_sync_client.cpp:499] protocol fault: failed to read stat response: Undefined error: 0

zsh: abort adb pull /system/build.prop"

Fastboot does not recognize that there is a device connected even when I boot it up by holding down the power button and volume up.

This is the WEIRD part. I made a new user on the device and when it switched to the new user, it popped up with the usb debugging notification AND "sdcard is mounted". But there's no sd card listed in the storage or in the files app. There's a slot in the battery bay for a micro sd card, but I haven't put one in and I verified that there isn't one in there. Makes me think that there might be some sort of storage drive physically installed somewhere on the motherboard.

I'm serious. ANY help would be greatly appreciated. This isn't even about why I was originally trying to do this. I've invested days into this and quite frankly just want to be able to say I've done it.

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