service interruption message on all our ipphones

[Hotsauce]

Hello all

all cisco ipphones in our organization display the following error message "service interruption" , until now i still can'f find the cause of this issue, and the only solution that i found to make phones working  is to change de "Device Security Profile" parameter from "Cisco 6921 - Standard SCCP Secure profile" to " Cisco 6921 - Standard SCCP Non-Secure Profile" on each of our ipphones, please check the attached screeshots.

everything has been working fine for years, but since two weeks ago, this issue started to appear on all the ipphones, and i dont now why

Sorry i'm just a beginner -_-'

Thank you very much for your help.

Regards

[b.winter]

Why did the phone have the "secure" profile in the first place?
Are you using encrypted calls internally?
Which value has the Enterprise parameter "Cluster Security Mode" in CUCM?

[Hotsauce]

Hello b.winter,

the Enterprise parameter value of  "Cluster Security Mode" is 1 , please check the screenshot.

Best regards

[b.winter]

What about my other questions?

[TechLvr · Accepted solution]

Cisco 6900 series phones reached end of  support in 2019. 
These phones come with a MIC (manufacturer Installed Certificate) that is only valid for 10 years.
Most likely, your MIC certs have expired. 
Once the cert expires, you can't use these phones in secure mode any more. But you can continue to use them in non-secure mode.