Polycom VVX 411 Signing out Users at Random

Hello Deleted 

First of all, try to contact your service provider or Poly account manager (Where did you buy the devices?) They will try to help you or point into the right direction in order to resolve your problem.

As my previous comment usually that kind of exchange error can be found in the logs of the phones.

You can try checking this Poly community post:

https://community.polycom.com/t5/VoIP-SIP-Phones/FAQ-How-can-change-Logging-Levels-or-use-Syslog/td-p/4741

I would recommend you to enable these ones for exchange issues:

app1=2 , pps=2 , sip=debug, so=2 , auth=debug  nisvc= debug  pgui= debug  curl=1

Since you are using an On-premise infrastructure you may review the release notes and admin guide of the device model and software version that these devices are currently running:

https://support.polycom.com/content/support/north-america/usa/en/support/voice.html

https://support.polycom.com/content/support/north-america/usa/en/support/voice.html

VVX 401/411

https://support.polycom.com/content/support/north-america/usa/en/support/voice/business-media-phones/vvx401-411.html

Also, you can review the following post about Microsoft services in 3rd party devices like Poly ones:

https://techcommunity.microsoft.com/t5/skype-for-business-blog/oauth-2-0-and-third-party-application...

I hope all this info helps you.