A possible solutiion is to open the Task Manager (Ctrl+Alt-Del) and under Background Processes click on the End Task button fior any Vegas Pro entries. This seems to be a common 'time-to-time' problem with Windows 11 and also happens with Microsoft Outlook for me .
The Task Manager solution works every time for me. It's a bit tricky because you need to attempt to start Vegas twice, then "end task" on the first instance of the background process "Vegas Pro". I made a workaround tutorial:
OP said that even after a reboot (assuming rebooting the computer), VP does not launch.
And since the OP does not have any additional information about the computer specs (checked profile) nor what version of Vegas is being used... I suggest that @Michael-Susca you read THIS and respond here with the necessary information from you in order to try and help you. Read "A", answer "B" and "C 10".