I bought our canalside house with moorings (which needed CRT permission and then developing) almost 5 years ago. It had been on the market for over 2 years...
I wanted a house with at least a 58 foot mooring, and back then there were typically 5 or 6 suitable properties (4 bedrooms, right price, reasonable location etc) for sale at any time across the country. Try Googling to see what the competition is.
I found mine by Googling "canalside houses with moorings". It was on Rightmove with no mention of potential mooring.
Also not many house buyers are boaters, so the mooring is only appealing to a small potential of buyers.
Hang on in there and someone will eventually buy it if the price is right.