Cannot open Code Editor for InfoPath

Question

Hello, I'm supporting an old legacy application that was created using InfoPath.

I opened the form (.xsn file) in InfoPath Designer 2013 and updated the project location to reference the associated .csproj file containing the C# code for the form controls.

After this, I press the "Code Editor" button in InfoPath Designer (expecting it to open Visual Studio 2012 with VSTA installed) but it fails with a small window that does not display the error properly:

Clicking on the "?" in the upper right corner of this dialog window opens the following new window:

I have spent additional time investigating this error without any success.

Any help or suggestions much appreciated!

Thank you!

victor