updated to 6.3.4.2, cannot open, soffice.exe not found

Actual message is ‘C:\ProgramFiles\LibreOffice\program\soffice.exe’ specified in the target box is not valid. I would be grateful for any help to sort this out.
Regards

What is “target box”? and why is “ProgramFiles” without a space between the words?

Are you trying to open LibreOffice using a shortcut? Can you open the program via the Start menu?
For reference, see: Techland: Windows Shortcut "name specified not valid" Fix