Looks like you have 2 problems:
You Rental Contract API seems to have fields that starts with a number, currently not supported, please unselect those fields from the API
And then it looks like you have an empty API defined, delete that one.
Then try to publish again.
Hi Erik
I have the same issue.
I have tried to keep it simple and just want to publish the describtion field from the Item table.
I did update the symbols before publishing