35118: MessagingServiceSid is required to schedule a message

This error occurs when you try to create a scheduled Message without MessagingServiceSid. To schedule a message, send the request through a Messaging Service and include the scheduling parameters in that request. If you want to use a specific sender, you can also include From, but the request still requires MessagingServiceSid.

• Your request included ScheduleType and SendAt, but did not include MessagingServiceSid.
• Your application tried to schedule the message by passing only From. Scheduled messages require a Messaging Service even when you want to use a specific sender.
• Your application passed an empty, misspelled, or malformed MessagingServiceSid value. A valid Messaging Service SID starts with MG.

• Add MessagingServiceSid to the API request whenever you set ScheduleType and SendAt.
• Create or select a Messaging Service, then resend the request using that service's MessagingServiceSid.
• If you also pass From, make sure that sender is part of the Messaging Service's Sender Pool.

• Message Scheduling
• Messaging Services
• Message resource API reference