Yeah I assumed you'd know to pour the IO solution into the salt tank so it could dissolve salt..... Try this, mix a 1/4 cup (dry measure) of Iron Out or Super IO in 2 gals of water and pour that into the water in the brine tank. Wait 2 hrs for the water to dissolve the amount of salt it should (6 lbs), then do the first regeneration. And if I were you I would repeat this process a second time with no water use between or during the 2 regenerations.
BTW, that 12 you had changed to 7 and then back to 12 is minutes of refill, and if you have a BLFC of .5 gpm or 1.5 lbs/minute, that's adding 6 gallons, meaning it's using 18 lbs of salt per regeneration, which is way more than the max (12 lbs) for a 1.25 cuft softener AND, adding my 2 gallons will probably cause the water level to rise too high. It depends on how much salt is in the tank, and my 2 gals could cause overflow out the elbow outside the salt tank so... don't add 2 gallons, mix the IO in like 1 gallon or as much as needed to get it all dissolved and into the tank without overflowing on the floor. OR pour the 1/4 cup into the water in the tank and stir it up there to dissolve it. Then you don't wait the 2 hrs either.