Pizzaboyo, The Amazon stone description says to pre heat 482 F. - 572 F. or 250C-300C.
Your oven I assume has a max dial setting of 500 F. Have you checked either the oven temp after an hour or the stone temp perhaps with an IR temp gauge. I wonder how hot the stone is really getting? When you turn on your broiler after max temp is achieved does the broiler go on? Some will not.
There may be work arounds to get your oven hotter but would be helpful to know the temps 1st.
That's a mighty thick pizza stone!!!!