The bowl has come loose from the base of the toilet in my motorhome. The bowl is porcelain and the base (with the flush valve) is plastic. Looks like I will have to remove the toilet and turn it over ...
Depending on brand, there may be a stainless hose clamp holding it together. Pull off the plastic trim piece and tighten the clamp. Be careful as there is a torque spec for it, something like 25 inch pounds.