With the move to offsite work in Inventor projects using a connection to Vault back in the office, the monitor setup may be different than at work. This oversight can cause some dialog boxes to be reported as missing. Or that Inventor seems to lock up when the Vault check-in dialog box that was moved to a secondary screen in the office is missing at home.
For Inventor, the missing check out dialog box is crucial to navigate to and open needed files from Vault.
The solution is to bring the open, but off-screen dialog box back into view.
When you press Alt+Spacebar then M, to move (with the keyboard arrows), the missing dialog box can be moved back onscreen. It helps if you know what side of the main monitor it may have been, otherwise, try first moving it to the right by holding the right arrow key on the keyboard, or the same for the left arrow.
You can also try holding the Windows key+Shift then press the left or right arrow keys as needed. That will pop the dialog box between monitors with each tap.
Once the check out dialog box is back on screen, Inventor will remember that position for the next session.