HI sir i am interested to fix your prestashop BO FO 504 error once contact me i will start your project immediately once we will discuss about project if you are not satisfied with my skills once visit in my profile where you can see my clients feedback for my work thanks.
ok I did not work with prestashop before but I may be able to help you here as it looks more like a configuration problem
just call me in and if I can find the bug there I'll get payed ok?