There are other reasons why a project may not open in Logic Pro for iPad.
This answer comes straight from the manual— and the conditions are even more nuanced than simply not having 3rd party plugins in the project or having bundled the project as a package.
In fact, it is rather easy to stumble in several different places here—
”Projects created in Logic Pro for Mac with any of the following features can’t be opened in Logic Pro for iPad (in such cases, a dialog appears telling you which features are present when trying to load the project):
- Surround
- Binaural panning
- Projects saved in folders (not as packages)
- Sample rates greater than 96 kHz
- Drummer Producer Kits
- Projects in which the primary ruler is set to time instead of bars and beats
- Projects starting at a position other than 1 1 1 1
- Arrange folders (with multiple tracks)
- External MIDI tracks (without External Instrument plug-ins)
- No output tracks
For more information about the individual features and how to remove them, see the Share projects chapter in the Logic Pro for Mac User Guide.”