Similar problem here, I started a Ritchies Festival Landlords Finest Bitter on Wednesday, 24 hours later all looked to be bubbling OK if a bit slow, 48 hours later all bubbling stopped, temp around 20C, gave it a stir. 72 hours later no more bubbling, checked the usual, reading about 1.022, anyway decided to throw in the hop pellets that come with the kit (instructions say after 5 days fermenting to do this), 10 mins later the yeast is working again :) a nice Krausen had formed a couple of hours later at which time I also added 1/4 teaspoon of yeast nutrient just to be safe.
I've read that some yeasts have been cultivated to respond better with hops present, but I've also read that hops can cause CO2 to come out of solution, but with a Krausen forming I'm assuming the former for now. I've no idea which yeast strain is included in this kit.
So another option might be to throw in a few hops to try and get it restarted :whistle: