Hello everyone 
I can not install the game on my external hard drive … Even FH3 I can not install it anymore … please help me 
If you can’t install the game, please check if you have enough space remaining on the hard drive.
Is there any error messages that appear when you try to install?
It does not show me any error …
In the selection list to choose your hard drive, the installation does not offer me my second hard drive
Un plug your Drive and use a different USB port
Xbox? Sounds like you external drive failed, or if like, just a cable failure.
PC not xbox
Go to Settings - Apps look for Forza Horizon 3 or 4 and go to advanced options and select reset then check to see if all parts of the game are on the same drive and not on different drives. If on different drives move all to the same drive