Yikes - locked out of mergAccessory

[Ben Rubinstein]

I've got a subscription to mergExt - hurrah.

I've got a Business license - hurrah.

I've been hoping to use mergAccessory for something (redpark serial cables). I 
did a test a couple of weeks ago, got the stack installed on a phone, 
mergAccessoryNames and mergAccessoryProtocols worked (on an old version of the 
cable), great. Then I put it aside until I had the hardware.

Now I've got the hardware, written my first attempt at a script, and when I 
try to use mergAccessoryOpenSession get an error

	Error: 634,0,0,external not licensed.

As far as I can see, the external is doubly licensed!

If I try to tell LC 8.1 not to do its own inclusions, but use the version of 
mergAccessory I've downloaded direct from mergExt, then I get an error about 
linking for arm64 failed.

So I seem to be stuck either way. Before I bother LC support, is there any 
simple gotcha I'm missing?

Many thanks,

Ben