Unable to add attachments to Knowledge Base Articles

We are on version 4.0.268.

After saving a knowledge base article, we attempted to add some attachments to it using the + sign. When we click the + sign, we are presented a “Choose file to Upload” window. After selecting the file to be uploaded, we clicked the Open button and an error popup window appears (Note: Outlook Pro 2016 is the name of the file to be attached)

The path is correct, otherwise we would not have been able to browse to the file.

How can we fix this issue?

Need to get on a call and take a look at this.

Just leaving a note for any future reviewers of this article…

We are on version 4.0.305.

We have been able to create knowledge base articles and add attachments without any issues since we have upgraded.