We have an on-premise SharePoint Server 2016 (Vers. 16.0.4690) installation with multiple web applications installed.
One of these web applications is FBA-enabled.
I can sign-in to the SharePoint site with Windows- or Forms-Based-Credentials through any browser (Chrome, IE, Edge).
Since a few days, out of nowhere, I get the following window, when I try to open a MS Word or Excel document from a library in this Web Application:
(Anmelden = Sign-In)
When I choose Windows-Authentication, the window just reloads. If I choose Forms-Based-Authentication, I can enter credentials, but I'm unable to login.
If I close the window, the document won't be opened.
In another web application, where FBA is not enabled, I can open documents without any problem.
The problems occurs on every client machine (equipped with Win 7 / Win 10 and Office 2016)
What I have done so far:
- Set "EnableADAL" registry-key on the client machine to 0
- Installed the latest updates on the SharePoint Server (Windows Server 2016) and the client machines
- Checked, that "Client Integration" is enabled in the web appliction
- Added the site to the Trusted Intranet Sites.
- Enabled IE Protected Mode for "Local intranet"
- Tried to open documents from Google Chrome, Edge and Internet Explorer 11
- Tried to open the documents from within the Office application -> same behavior
Has anybody an idea, how I could solve this?