Can't really guess what happened exactly. But since you mentioned it did once turn ON and show the "0mA" and then it went sour, something did happen that's causing it to not boot up into firmware.
To expedite fixing this unit, I will need you to return this unit to me and I will look into it and repair it. Please include the OLED you used. I would always encourage you to use a HEADER for the OLED instead of soldering the OLED directly. And use it with the OLED case (you can print your own or I can send you one that's less than perfect and cannot be sold in the store). That's because the OLEDs can actually be pretty fragile, and it's much easier to replace it in case it breaks. Also the case ensures you always insert the OLED the right way and not shift the pins in the header.
Please reach out via the contact form and I will give you details for the RMA.