The TLS version used by your SIP endpoints is lower than the one configured for your account. It's highly recommended to upgrade your SIP endpoints to use TLSv1.2. Otherwise, you can opt in to use deprecated TLS versions in the console. By default, only TLSv1.2 is allowed.
SIP/TLS version is lower than the allowed
Upgrade TLS version or configure your account to allow all TLSv1+ in console (Voice → Settings → General → Allow Deprecated SIP/TLS versions)