The ContentVariables Parameter is invalid

The ContentVariables Parameter is invalid.

• The ContentVariables Parameter is not a JSON String.
• A ContentVariables variable placeholder is improperly formed e.g. {{example}.
• A ContentVariables variable placeholder is an "empty mustache" e.g. {{}}.
• The ContentVariables field is defined with improper formatting at time of send.
• The ContentVariables field contains a variable that was set to null at time of send.

• Review the documentation on how to use Content Variables with Content Templates.
• Validate the ContentVariables Parameter, it must be a JSON String and be properly formatted.
• Make sure all ContentVariables are defined and have a valid definition at time of send.