Album Art not showing

[Wiggers]

I have Minim 2.2 installed on a Synology NAS and I use an Onkyo TX-NR818 to play tracks. I used to use Synology Audio Station as the DLNA server and that displayed album art. I then tried the free Minim server and there was no art being shown. I thought maybe I had to have the paid-for licence for that feature but it's still the same. I can see the art on my phone with HiFi Cast so why doesn't it appear on the Onkyo please?