Hello Andreu.
This error is common enough, when r3 instances are recovered or migrated and the transfer path is not recovered/migrated as well.
The error message states that it´s looking for an export file that needs to exist because it´s a dependency of your app. Every app you install in r3 creates a file in the transfer path - this file is important as without it, you cannot create exports.
If you did recover or migrate your r3 instance, do you still have the source? (ie. a backup source or the original server directory)
