I am a complete NEWBY on this, but my experience with pumps and sand is.
Either your below the water table, which means it needs to raise. Or it is
an new well and the sand is stopping the pump from turning. Then only
higher currents will do the job. As for cleaning out the bottom of the
casing, once in sand,,,,, I have no experience. You might try dumping a
1000 gallons of water down the hole and then see if you can get it to run.
Once the pump pulls a suction the flapper on the bottom should open and then
the water would flow in and the sand out.
Sorry that I do not have the answer in my back pocket.