Error in "Synchronize Products with CPQ" Integration Map page

Summary:

Getting "400 bad request" error when we open the "Synchronize Products with CPQ" Integration Map page.
Please find the error details below. 
Status: 400
{"title":"Bad Request","status":"400","o:errorDetails":[{"detail":"The response from the target application couldn't be parsed. Verify the integration map and try again. (ZCA-210427)","o:errorCode":"ZCA:::ZCA_DATA_INTEG_CNNOT_PARS_RESP"}]}

We want to map the custom fields to CPQ products. 

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