I have the issue once again. This time I have been unable to get the audio signal nto cubase via anything other than the in-built mic.
This is now getting extremely frustrating.
I have tried 2 interfaces, Behringer UA202 and Realtone cable (rocksmith) from ubisoft.
I can get audio from Realtone into Tonestack, but not cubasis, I cannot get audio from UA202 into anythinbg anymore 
However audio output through UA202 seems to be working fine.
I wasted 3 hours trying to get this working so that I could play with my new iRig Blueboard, instead I was rebooting, starting things in different orders, all to no avail.
I very nearly deleted cubasis. Not entirely fair as just because cubasis is the hub for music making it gets the blame for issues that are not under it’s control.
There has been a recent update to audiobus, could this be to blame ? or could it be my fault for trying to use the realtone cable, and my iPad is now confused with audio input ?
Any help or ideas welcome