Make absolutely CERTAIN that the "dry/flush" knob...
Is turned ALL the way to flush mode. If it's only part way, you'll get little or no flush water.
Check all the holes in the underside of the rim of the bowl...it's possible that a sea water mineral buildup has clogged 'em. To check whether the problem is in the pump of the bowl, remove the hose from the bowl and flush pump the toilet. If there's a blockage in the bowl rim, water will flow out that hose.
Which brings me to another thought: I don't suppose you've just finally gotten around to installing a vented loop in the intake--which should have been done when the toilet was installed--but put it in the wrong place (between the thru-hull and the pump)? 'Cuz if you have, the pump will have a hard time priming, which would prevent your getting any flush water.
If none of the above, call Raritan tech support at 800-352-5630 x 6 and ask them to trouble shoot it.
I don't THINK the tank product had anything to do with it. Most tank products are intended to be flushed down the toilet...'cuz they may not make it to the tank if you put 'em down the deck pumpout fitting. However, I wouldn't leave any sitting in the bowl. That doesn't accomplish anything and can damage the joker valve.