Often with a tubeless tire that has gone flat the bead is broken and it is a bit of a pain to get the bead to reset to pump in air.

One trick that can work is to tie a loop of rope around the tire with a good piece of wood under the rope. Twist the stick around to sinch up the rope and this will usually squash the tire all around the rim so the bead sets and allows the air to be pumped in to inflate the tire. Unwind the rope and remove it as the tire inflates.

jtk