Hi,
Are you sure that the popup is not because you already have the parameter "?popup=1" in your current URL ?
With the "redirect to checkout" ; is it working when you add the first product ? What URL do you have ? Does your "force menu on checkout" right configured ?
In order to tell you what you have to change in your configuration, first we have to know your current (HikaShop mostly) configuration.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.