TDP is working good today morning. But suddenly started not working and then not able to open. Restarted the machine and re install the TDP still not able to open. No error message. Just showing the opening window.
I would look in event view under applications to see if you can see error.
Has any new policy been applied to your pc or updated virus protection? Sometimes this can be a problem.
If none of these help, add /log=all to the shortcut on your desktop, start TDP. Then look for toad.log in the app data dir and see what is in the file.
App data dir
C:\Users%Profile%\AppData\Roaming\Quest Software\Toad Data Point X.X