See page 2 of this thread:

https://answers.microsoft.com/en-us/msoffice/forum/all/microsoft-dynamics-nav-wont-launch/a2c7ae90-d308-4ab6-87ff-318d3dd3988e?page=1

Specifically this response:

After some extensive testing it seems the Office updater is the cause of the problem.

I’ve managed to reproduce the problem several times running the Office updater, waiting while it supposedly downloads updates (which it doesn’t, because there isn’t an update) WHILST NAV is running.

As soon as it finishes the update check and shows you the message: “Updates were installed” (without updates being installed) the Office register values are deleted from the Office registry keys in:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App

Paths\.exe

HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\App

Paths\.exe

(as far as i could find)

As previously stated NAV needs Excel.exe key to have values to start, OR the

Excel.exe key needs to be deleted from the registry.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\App

Paths\excel.exe]

@=“C:\\Program Files\\Microsoft

Office\\Root\\Office16\\EXCEL.EXE”

“Path”=“C:\\Program Files\\Microsoft

Office\\Root\\Office16\\”

“UseURL”=“1”

“SaveURL”=“1”

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App

Paths\excel.exe]

@=“C:\\Program Files\\Microsoft

Office\\Root\\Office16\\EXCEL.EXE”

“Path”=“C:\\Program Files\\Microsoft

Office\\Root\\Office16\\”

“UseURL”=“1”

“SaveURL”=“1”

I’ve also managed to fix this by doing ‘quick restore’ of the

Office installation, which restores all the values in the Office

.exe keys.