Sorry. There is not an MIT online app inventor site where you can build a service app (an app that will run in the background). The service (task) site was removed a long time ago.
Is this what you are trying to do You downloaded the services branch and compiled it on your own computer?
The branch can be found here:
thequixotic/appinventor-sources
MIT App Inventor Public Open Source. Contribute to thequixotic/appinventor-sources development by creating an account on GitHub.
The README has all the instructions needed to compile the sources, however this code is over four years old and can not be expected to work with modern extensions and the Companion.