They're there: you can be sure of that.
You can see them and locate them best from behind by sticking your head under the back shelf and looking upwards to the hinge of the back rest of the back seat. There are two pairs for two different child seats.
Once you've seen where they, you can more easily locate them from the front by sticking your fingers through the (non-existent) gap between the seat base and back and wriggling them around.
Then it's just a case of ramming th e isofix bayonets through this same non-existent gap.
After doing it a half dozen times it becomes second nature
But I'm not the slightest bit surprised you're not finding it easy.
Others will come in with a better description I'm sure