Please refer to this documentation for what data source should look like:
https://cloud.google.com/retail/recommendations-ai/docs/record-events#datalayer-gtm. You most likely have an incorrectly formatted data source - this is usually the cause of the issue you are experiencing
If you use a data variable, it needs to be in the Cloud Retail format, and it needs to be a JSON object (of the form {}).
You send the tag id (not container id) to my email