iModel file - Views disappear when processed by Navigator Mobile Publisher

Anyone come across this?

I have a 5MB Microstation file (contains a zMapping reference file) which I previously was able to view on my iPad Air via NMP.

It looked terrible - garish colours- and all the views were not as desired, so I went back and changed the original file to simplify the colours. Tried to delete the existing saved views, then created 18 new ones, published it to iModel with Microstation v8i SS3 and then published it again using NMP.

When I load the file either within NMP or on the iPad it is an 'empty' file - no views there to click on and load.

Any thought as to what can be the problem / how to solve it? I can see the file and all its views fine in a 3D PDF using the 'Print to 3D' function.