I don't like/use tire sealant. One reason being that it eats wheels (both steel and aluminum), another being the mess when you need to remove the tire.
Put water and a bit of dish soap in a spray bottle, shake to mix. Inflate the tire and spray with the soap solution, watch for bubbles. Spray the valve stem, bead area, everywhere. You may only need a new valve stem, it happens. You may have a small puncture. You may have a bead leak.
I have a HF hand truck and every time I needed to use it, the tires would be flat. The tire beads were such a loose fit on the wheels that it wasn't difficult to figure out that was the problem. Without removing the tires, I applied RTV silicone to the bead area of the wheels as quickly as I could then inflated the tires. I pushed the tire to one side to access the wheel, did one side, repeated on the other side. The tires have held air ever since. I used the black, oil resistant, Permatex RTV because it's what I had on hand but any RTV silicone probably would have done the job. I've also used RTV to seal the beads on lawn tractor tires in the past.