For canvas I make my own profiles based on the canvas after the satin gloss varnishing. That makes a difference in gamut. Another issue can be that the media preset recommended by the printer manufacturer is not optimal in ink use, the canvas might allow more ink which could improve the gamut. Try another media preset, for an art paper for example. Color management with Macs, Adobe Software and printer drivers has been troublesome over the last years. I'm not an expert there but stick to version 2 profiles and read what can be wrong in the threads on that subject on LL's color management forum.
met vriendelijke groeten, Ernst
Dinkla Gallery Canvas Wrap Actions for Photoshophttp://www.pigment-print.com/dinklacanvaswraps/index.html