I think this might help:
The log shows a PUT-call. Meaning your importapp attempts to place an object on your exportapp. Probably not your idea.
To get started easily, in your exportapp rightclick on an entity, select ‘Expose as REST service’, click Select and create a new Service ‘MyService’, add your entity, at ‘key attribute’ select an attribute that is unique. Check all operations and click ‘OK’. Solve the Access rights and run your app. There you go, your service is fully published.
Check the result on <yourappsurl>/rest-doc/. Click ‘GET’, ‘Try it’ and ‘Execute’ and look at the curl. Copy the location, something like:
in your importapp, in the REST-call activity in your calling microflow, at this to ‘Location’. Save, Run, trigger your microflow and the rest call will receive your data.
To map the received data to your importapp’s domain, copy-paste the importmapping that got automatically created from your exportapp to your importapp and in your rest-call activity on the last tab ‘Response’ select ‘use import mapping’ and select it. Save, run again, trigger your microflow, now the data is imported and stored in your importapp.