One cannot RDP into the VPS unless another person logs off.
Previously it was possible to login via RDP even if there were two people currently logged in, RDP used to ask if you would like to disconnect or force disconnect.
One can still login via direct console with no issues but not via RDP without having another person logged off.
To increase the maximum number of simultaneous connections by using the Local Group Policy Editor:
gpedit.msc
\Computer Configuration\Administrative Templates\Windows Components\Remote Desktop Services\Remote Desktop Session Host\Connections