> Recognition of the device on Windows 10 is most likely the driver issue

Indeed, I have had this problem as well. Here is how I solved it, Tdawg , see if it helps:

* Open Device Manager
* Pixel 4a is listed under Other devices and has a yellow exclamation mark
* Click Properties > Update driver > Browse my PC for drivers
* Select Android\Sdk\extras\google\usb_driver
* It asked me if I want to install SAMSUNG Android device for some reason
* Click Install
* The driver is installed and Pixel 4a appears in Device Manager under Android Device > Android Bootloader Interface
* `fastboot devices` lists one device and `fastboot flashing unlock` works