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 RAS Console.
Misconfiguration of VDI provider. Max connections value should be increased:
Please adjust the Max connections value in RAS Console → Farm → VDI → 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.