Just need to force it a few times........
When you get 'check' light it is because propane flame did not light. It did not light due to lack of propane flow (empty cylinder...you don't have tanks)
Swapped cylinders and you have established flow to water heater and stove but not to section of propane line to fridge gas valve/burner.
Reset fridge....try gas again.......several times until propane lights
Don't you have an auto changeover propane regulator where both cylinders can be valved in and it swaps from empty to full tank so no loss of propane flow?