[FTC]: ZTE Phone is not detected on PC

[ArtemusMaximus]

We are finally at the point to start working with Android Studio, but I discovered we have serious problem. We have 2 ZTE Speed phones and both of them are not detected on my PC.
Here are troubleshooting steps I've done:
~ Tested my Moto G phone, it detects successfully
~ Check Device Manager - phone is not listed and no unknown devices present
~ Tried on different computer, still not detected
~ Tried different cables, still no luck

Not sure if it is related, but there are couple more nuances:
~ when connected to USB charger, phone, while charging, does not register that it is charging.
~ if I plug phones to charge while it is powered off it enters in Start up and Reboot loop.

Any ideas how to resolve these phone issues?
If we can't resolve this issue, is there a way to load custom programming via SD card?