The bootloader of my Dutch (not verizon) Google Pixel 3a won't unlock. I easily get it in to Fastboot Mode and than promp it from Windows Powershell in the Platform Tools share. After this I command the fastboot flashing unlock but I don't get a message on the device to proceed. I get nothing.

I need to downgrade to install Touch. I unlocked the Developers options, enabled OEM unlocking and USB Debugging. The Windows 10 is fully update. ADB functions.

Where do I go wrong?

Probably this question has been answered already, but I couldn't find it.