Hi,
Please have a look at the UR28M manual on page 31 that shows up with a connection example for the iPad:
Some important notes:
- Please make sure to use Apple’s original adapter (Apple iPad Camera Connection Kit/ Lightning - USB Camera Adapter) when connecting the audio interface with the iPad
- In case, you run an older UR28M device (before Oct 13) it might be required to update its firmware UR28M Updates and Downloads | Steinberg
- Give it a try to shut down the iPad (“slide to power off”) and restart the device before connecting the audio device
Hope that helps,
Lars