did this issue start after changing the tank?
the 1st thing you check (and you should always check when changing the tank) is that the o-ring that seals the connection didnt come loose get lodged in the wrong part

the coupling (the brass fitting on the end of the hose) should have NO RUBBER PARTS when you look in it you should just see brass and a chrome center

all the rubber parts are on the tank side of the connection but 1 of them can come loose and cause a hard or no-start or just make the machine run crappy in general

if there is a rubber ring in there CAREFULLY tap the coupling face down on the counterweight to knock the ring loose and it will fall out

double check the fitting on the tank
there should be a square cut o-ring on the outermost part of the inside and a round (normal) o-ring in a bit on the inside of the tank's valve

this sounds like its your issue
if the model j was bad it would most likely flood the engine
you would get a heavy propane odor and ether woulndt help (i dont use ether ever)
the fact the ether fires it tells me the spark is there although id prefer to visually inspect this

also proves the timing is ok

check that coupling for an errant o-ring
this is a very common cause of no-starts and i make a good deal responding to them

USE HEAVY LEATHER WORK GLOVES AND EYE PROTECTION WHEN WORKING ON PROPANE OR JUST CHANGING THE TANK
PROPANE REFRIGERATES AS IT BOILS (at room temperature and no longer under pressure in the tank)
TEMPERATURES ARE WELL BELOW 100 DEG BELOW 0 (its boiling point is -44 the rapid expansion causes refrigeration thats much colder)
IT WILL BURN YOUR SKIN AS BAD AS FIRE WILL

this site also blocks URL's and emails so you have to do a lil editing to your links
like this:
youtube.com /watch?v=BqeCqfEkFPQ
or
youtube DOT com/watch?v=BqeCqfEkFPQ

if you need help my email is in my profile