Try this:
I faced the exact same problem and restarting my machine did not help. But i did one thing. I left the laptop for some time (it was night so i thought id attend to it next morning).
Next day i searched for the appdata folder in my laptop like this:
On windows OS, right click on the windows icon and click on run - a small dialogue box appears
type %AppData% on it and click okay
It shall take you to this file path - (username)>AppData>Roaming .... (I couldn't find it manually earlier - and this was a relief!)
Go to the zoom folder and click it open. In the meanwhile, keep your desktop zoom app open (This is important as zoom needs to be open to convert the file when you finally find it - You WILL find it, don't worry.)
In the Zoom folder, open the bin folder.
Search for the file named zTscoder and double click it. (LIke i said, make sure your zoom desktop is open - this is the zoom icon that appears on the laptop's taskbar.)
It shall take you to the folders/folder of recorded but not converted meetings. (Tears of JOY!)
Double click on the file you wish to convert and zoom shall convert it.
Hope this helps everyone who reads this discussion.