I encountered this error the other day and hadn’t seen it before:
When starting any office program by opening a file, the user saw: “There was a problem sending the command to the program.” Then when dragging the file to Excel, the file opened fine. What the heck?!
Turns out you have to turn off something called DDE (Dynamic Data Exchange) in the settings. This Microsoft KB article details the problem.
Go to the Office app in question and go to the Options. From there, click on Advanced and make sure “”Ignore other applications that use Dynamic Data Exchange (DDE)” is UNCHECKED like below in my version of Excel 2016.