I have a user that can open and edit a document in SharePoint Fine. She then does a "Save AS" and it works. However, if she opens and does the same thing with a second document, she gets an endless prompt for her credentials.
Also, when I open using the "Edit" option in SharePoint, it opens in Excel ok. But when I try to save as, I get the same prompt.
This also happens for me (admin) when opening a document using the edit option. It prompts for my credentials on save.
Why is she able to open in SharePoint and "save as" once OK, but the second time she gets a prompt?
This is for an on-premises installation of SharePoint 2013.