Mosaic overlap and other issues

I have used Telescopius to plan 2 recent mosaics, to be copied into ASIAIR and then processed in PixInsight . Both sets of data have failed. In Telescopius, I framed the area using 4 panels with a 20% overlap. Is 20% minimally adequate? I didn’t use the ASIAIR import feature because I don’t have a camera rotater and so I just typed the Telescopius co-ordinates into the AIR (triple checking them). The frames looked good and in the correct/expected areas as they came in.
But in PixInsight, using WBPP to stack and register the images, I got the dubious error message “Unable to find an initial set of putative star pair matches”! OUCH! To me this sounds like insufficient overlap (but I’m not sure). That’s why I wonder if 20% is enough.
Is anyone experienced with problems like this? Advice appreciated, it’s especially tough when a project fails and you don’t know the reason!