I wrote myself a little .net c# program to run CSOM commands on some SPO lists about a year ago. That worked fine until yesterday. The program opens the 2 factor authentification process as always and goes through it as always but after the last step when it usually shows “Signing into Sharepoint” that page appears for a millisecond to then show: 

Browser not supported

Use Microsoft Edge or Google Chrome or any other browsers mentioned in this documentation:

Now did my SPO admins tinker with it or was it Microsoft that changed something? How can I fix that. Can I force the AuthentificationManager to use another browser runtime?

Any help is greatly appreciated.

​I wrote myself a little .net c# program to run CSOM commands on some SPO lists about a year ago. That worked fine until yesterday. The program opens the 2 factor authentification process as always and goes through it as always but after the last step when it usually shows “Signing into Sharepoint” that page appears for a millisecond to then show: Browser not supportedUse Microsoft Edge or Google Chrome or any other browsers mentioned in this documentation: Now did my SPO admins tinker with it or was it Microsoft that changed something? How can I fix that. Can I force the AuthentificationManager to use another browser runtime? Any help is greatly appreciated.  Read More

​