You are using the FREE copy of Studio One PRIME. As this is a FREE version of the software, it comes with several limitations; one of which is the number of tracks that can be recorded at once. This is what is effecting your session and the root of your issue. You are trying to us an 8 input interface with software that is limited to recording 2 inputs at a time. If you take the DEMO version for a test drive, you will be able to use all of your interface's I/O.