Modern Authentication kills Exchange Connection

[Martin Front]

Hi,

we´ve activated Modern Authentication on several companies without any issues.

Yesterday we activated for a new customer with 20-40 users since we´re preparing for MFA and don´t want to use App-passwords.

Anyway, now we have a user with Outlook 2016 that can´t sustain the connection to Exchange Online as long as Modern Authentication is activated in the registry, as soon as we change the registry to inactivate MA the connection to Exchange Online is stable and works like a charm but when we´re activating MA again the connection to Exchange Online establish but after a couple of minutes it don´t have any connection towards Exchange Online anymore. 

If the user restarts Outlook it works for a couple of minutes but once again the connection "kills"..

Have anyone of you noticed this before and how did you solve it?

//Martin

[#2]

Modern auth needs to be enabled on the server-side as well, which is not done automatically for all tenants, so check for that. And check the sign-in logs for any related events.

[#3]

@Vasil Michev It is activated on the server side, otherwise it should not be in used for Outlook.

Where can i find the log in logs?