UPDATE – The bug was fixed in version 1.0.3 of the Control+ app
When you are building the LEGO Technic 42100 Liebherr R 9800 set the app has a verification process built in after every batch of bags. This is a great addition because you can see whether the motors built in are working correctly or not.
Unfortunately there’s a bug in the current version as of 05/10/2019 (version 1.0.2 on both Android and iOS ), after the second batch of bags at page 367 you should only have one XL motor (color code red) connected to the hub in the superstructure.
When you try to run the test it won’t connect, here’s how it looks like:
The solution is to connect all 3 remaining L motors to the hub. After that the second test will run properly (it will only test one L motor connected to port 1).
After the test you can disconnect the 3 L motors.
At the third test you already should have all motors connected to the second hub based on the instructions so that will run properly, just like the fourth test.
If you have any questions or have a different experience please let me know in the comments.