Problem with controlling Signia hearing aids from my Apple watch

When I ordered my Pure C&G T IX hearing aids, I was told by a Signa rep that although the Signia app couldn’t be accessed directly by my Apple phone there was a ‘workaround’, by which I would be able to control the volume, etc. from my watch. I’ve just been in touch with Signia, who say that this workaround has been withdrawn by Apple.

Why is this, Apple, and can it be restored please?