I wonder if he misses his meal time companion? I think there is an element of competition when two or more dogs are fed together.
I always have a abit of a routine around meal times for mine -if I am having issues around lack of interest in food.
Which isn’t often, I might add.
Their evening meal is given after we have eaten and taken plates through to the kitchen. Dogs bowls clatter out onto the cupboard, kibble goes in, I make a big show of literally scraping in a tiny bit of say, gravy, mash, veg. I shout to DH, have you left anything for the dogs? bring your plate through please. Even if there is nothing on it I will give it a good noisy scraping into their bowls. Dogs are waiting in their baskets watching and waiting, eyes on me. Kettle goes on, for a cuppa, make tea, trickle a bit of boiling water onto kibble, and I make a big show of mixing it in and sniffing, if DH is in the kitchen I make him sniff it too and we agree it is a very good meal!!
Dogs outside in usual positions, one two three, sit, wait, get it, and it’s gone in a flash!
It’s all absolute kidology, but I swear because I have fussed, sniffed, and made them wait for it - it’s the finest food in dogdom.