Check out the documentation here: https://docs.mendix.com/howto/integration/publish-rest-service
Section 4 describes what you should do
I think your page parameter and microflow parameter has does not match.
Please check your data view entities from where you call that microflow and check the parameter also.
And please go through the following link, It might help you:
When a client calls your REST operation, the microflow nees a Projecto. Where should the value of that parameter come from?
You have no query or path parameter. Also, your microflow expects an object?!
I’ll suggest you to add the projecto id as a path parameter. In your microflow you need to expect that parameter as an argument. Then you retrieve the projecto object via xpath.