The virtual machine isn't powered on automatically when users start a desktop published from it, error The remote computer is already in use by another user is displayed.
However, it's possible to start the VM manually from the RAS Console.
Misconfiguration of Provider settings.
Max connections value should be increased:
Please adjust the Max connections value in RAS Console → Farm → Provider → Select the appropriate provider -> Agent Settings.
It should match the state of the hypervisor and your needs - if you have say 400 VMs on the hypervisor and expect all of them to work simultaneously, please set Max connections to 400 as well.