I changed PC's a while ago and since then, I'm having USB issues: flash drives function relatively normal (although I can't create boot images on them), but some USB devices just aren't recognized.
After trying the same USB devices on my laptop, they're being recognized instantly and work as expected.
So try to connect the stand-alone board to a PC that has never seen a CH340 (or CP2104, depending on the used on-board USB-UART convertor) and see hear/see if the convertor is recognized.
If nothing happens, there's a chance the USB - UART convertor is dead and hanging up your ESP.
You could just remove the convertor IC from the board and program the ESP in the old fashioned way, but it's cheaper to just bin it and buy a new WeMos.
When you're new, don't start with a separate ESP (ESP-01 to ESP-14) module.
Get yourself a proper development board: NodeMCU - WeMos D1 - WeMos (UNO form factor) - Witty Board
ESP power requirements are 3.3V±10%@350mA
The ESP8266 IS NOT 5V tolerant on ANY pin (see item 5.14 on page 25 of the FAQ)