Phone Numbers must be in E.164 format. E.164 numbers are formatted [+] [country code] [subscriber number including area code] and can have a maximum of 15 digits.
<Number>
noun inside your
<Dial>
TwiML instructions is not present
Check the format of the phone number inside your <Dial><Number> TwiML.
Verify that the number is in E.164 format:
In your TwiML instructions, the phone number must be between the opening and closing <Number> tags, which are nested within <Dial>'s opening and closing tags:
_10`<Dial><Number>`+15555555555</Number></Dial>
If you are attempting to <Dial> an SDK end-user, ensure you're using the <Client> noun inside your <Dial> tags.
If you are attempting to <Dial> a SIP endpoint, ensure you're using the <Sip> noun inside your <Dial> tags.
For more information, read the <Dial> docs.