Fastboot connection problem

I am trying to install Lineage OS 16.0 on my Moto 4X. I unlocked the OEM bootloader. But when I enter the command 'fastboot reboot bootloader' it shows
'< waiting for any device >'. There it stays until I break.

The next day it suddenly worked and I booted TWRP, install Lineage OS, G-Apps 9.0 micro and started the phone following the instructions at https://wiki.lineageos.org/devices/payton/install.

Lineage seem to work fine, but the G-Apps are nowhere to be found. I remember during the installation there was an error like 'can't access date/media., such a Directory does not exist' but it worked, or I thought that it did. I wanted to reinstall it all. Now I have the same problem again.

C:\adb>adb devices

List of devices attached

ZY224KGGGC

device



C:\adb>fastboot reboot bootloader

< waiting for any device >

USB debugging is enabled, the drivers on the PC are the newest from the Motorola website.

I used every USB port on my PC.

I tried my PC and two other laptops, all Windows 10.

Also I tried CMD, Powershell, and GIT-Bash for the commands. It’s always the same response. So I don't know what to do right now.

Does someone know where that problem came from?