Hello, I have an error on the Manage Design page (admin.php? Page = fpd_manage_designs). It does not load the css and js, since it was working correctly, which could be, if you can help me please

Can you disable any recent plugin you installed before you had this issue or even disabled all plugin and theme and allow only FPD if this work then it should be a plugin conflict causing this. If not open a ticket with the support the can better assist you.