customizer not working

the cusomizer editing stop viewing : sometimes after loading the page several times the page loaded but the editing does not view on the fly but when publishing the site updates properly , but I need to see the editing on the fly (in the customize mood) I did almost all procedures to solve this problem : remove all plugins and install them again ,delete cash for site & browser finally I changed the theme and get back to the same one , but the problem insist So what can I do ?? please help! Thank you