Extension showing Authentication failed

I am new to asterisk.I had configured two extensions in asterisk but those extensions are not registering with softphone they are showing that Authentication failed. To resolve this problem i had changed from Nat=“yes” to “No” also but still its not working. Please give me the solution its urgently needed. Tkanks in advance.

With Regards,

Venkatesh Kandepu.

Devices, not extensions, register with Asterisk.

You have not provided nearly enough information to assume this is the result of anything other than misconfiguring the authentication data in the phone.