Debugging
Probably doesn’t help you now, but I would have checked in and asked for help before you desoldered the MCU. It’s hard to desolder the MCU and it’s possible you damaged a pad or trace.
What MCU did you build with? When you plug in the board, does the MCU get warm near the USB connector?
What MCU did you build with? When you plug in the board, does the MCU get warm near the USB connector?