IP Phones don't register anymore

[Eng.AymanSabry]

Dear All 

I'd like your help in my issue i deployed CUCM 11.5.1.16900.1 with CMS 2.6 and i used CA to upload certificates 

Conference bridge is fine spaces are fine.

CUCM is set to mixed mode and i can't register any IP Phone with auto-registeration and manually also

i reseted all the phones and still no luck i tried different CUCM version 11.5.1 unrestricted in non secure mode and all ip phones register 

Please any idea which can help me out

[Mohammed al Baqari · Accepted solution]

Hi, on the phone hit settings > security configuration > ITL > hit **# >
More > Erase. See if it works.

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