63021: Channel invalid content error
PROGRAMMABLE SMS
ERROR
Message contains content that is rejected or unsupported by the messaging channel.
- Unable to upload the media used in the message because it is not supported by the messaging channel.
 - Message contains components not supported in selected messaging channel
 - Length of the the template text exceeds the allowed length of 1024 for WhatsApp.
 - Length of button text exceeds maximum length of 25 characters for approved WhatsApp templates or RCS suggestions and 20 characters for in session WhatsApp templates.
 
- Inspect the media files being sent and confirm their MIME type is in fact supported by the messaging channel.
 - Confirm message components follow character limitations, proper formatting, and channel specific rules mentioned in docs if applicable.
 - Confirm WhatsApp template sends do not exceed 1024 characters, which can occur when placeholder text substitutions or translations are too long.