I have recently edited movies using my Vegas 21 but when i save it it says it is a Vegas 19 and then when I reopen the saved edited video it will not run.
I'm guessing Windows has VEG assigned to 19 instead of 21. Tell Windows to use VEGAS Pro 21 when opening a VEG file.
Out of curiosity, are these edited videos rendered out or are they still just project files? If the former, the files themselves may be getting corrupted in the rendering process. If the latter, I second what @jetdv said.
Tell Windows to use VEGAS Pro 21 when opening a VEG file.
To do this, go to Default Apps (a Windows app), type '.veg' in the search field and click on the VEGAS Pro result. A window should open showing the default Vegas Pro version currently being used (presumably VP19) as well as other VP options which can be selected and the Set Default button then hit to change the default to the preferred VP version (21 no doubt). This means that any .veg clicked on will open in VP21 rather than an older version such as VP19 if that is currently set as the default VP app.
Windows 11 used.
Or just right-click the VEG icon in Windows Explorer, choose "Properties" and then click on "Change..." to the right of "Opens with..."