Importing Postman Collection into ZAP: "request field is not present"

Question

I'm trying to import a Postman collection into OWASP ZAP, in order to do some API pentesting. However, ZAP is giving me a hard time to import the collection. I have removed most of the variables, exported the collection as a json file from Postman, and when importing in ZAP defined the remaining two variables, but it still gives me an error. In the Output window of ZAP it says "Failed to import : request field is not present". And the lastly: "No item could be imported from the collection. Please check if the items exist and if they are valid.". Any idea what could be missing? Its a perfectly fine working postman collection, so Im at a loss.... Txs!