Transducer Won’t Read Through Hull

Cored hull was my guess while reading your description of the problem, even before you mentioned it.
'Dunno how Novurania hulls are built, though.
But if that's the culprit, I think you'll struggle to find an alternative that works without drilling a hole and fit a through-hull xducer...

PS: I'm saying this because I've also an Airmar P79 in my boat.
Fitted right along the keel centerline (against installation instructions), where the grp is thick as a brick, sealed to the bottom with silicone which supposedly isn't as good as glycol for best results, and it's still working just perfectly after almost 20 years!

Either core or some voids in the laminate

Problem with transom mounted xducers on dinghies is that sometimes if you pull it too far over the chock, the rear chock can break the bracket.

Since sealing the ring to the bottom and fill with glycol before fitting the P79 is a bit of a PITA, if the interior of the hull is as smooth as usually Novuranias are, I would first try moving the transducer around without any preparation at all.
I mean, it will never give an accurate reading without a proper installation of course, but if by moving the transducer around with its bottom as attached as possible to the hull you find a spot that gives "some" reading, you're good to go.
And don't dismiss the exact hull centerline, which might well be more solid.
As I said, that's against the manufacturer recommendation, but it has worked just fine for many years in my boat.

Put the transducer in a ziploc bag of water, move it around the inside of the boat and see if you can find a place for it to read through, the only area might be center bilge on the pad.

You really don't need to bother with the water bag.
As I said in my previous post, you can just slide the transducer around the hull interior, and if/when it will meet solid GRP, it will read through it even if there's a very thin layer of air in between. It won't give an accurate reading, but you only need to find the right spot where it does work.
Tried and tested with the very same transducer.

It all depends on how smooth the interior hull surface is - and I half recall it's pretty smooth in Novuranias.
Besides, in a normal installation with glycol there's no need to put the transducer as much in contact as possible with the GRP, so it stands to reason that it stop reading after the fluid ran out.

Anyway, the water bag can only improve the transmission, of course.
I would just keep it as a plan B if the dry test gives no result.

I can't be positive about your Simrad display, but many transducers are actually built by Airmar, and they just come with the appropriate plug depending on the display model you must used them with.
In fact, also the B60 that CaboFly mentioned is an Airmar transducer, and aside from being available for different displays, it also comes in two version, both flush with the hull bottom but internally tilted inside the housing, at either 12 or 20 degrees.
And supposed to work well with a hull deadrise from 8 to 15 deg or 16 to 24 respectively.