Hi Laura,
When you look at the ion mobility heatmap, do you see a horizontal purple band indicating the IM range that was used in extracting the chromatogram? If not, you've not yet assigned a mobility value to your precursors, which is why nothing shows in the report.
If that's not the case, I'd be happy to look at your data (use Skyline's File > Share menu item, and include at least one of the mass spec files).
Thanks for using the Skyline support board,
Brian Pratt