Using links instead of button

All pros, i humbly seek for your advice, let me try to make it as short as possible

my pricing table plugins ( pricing table by supsystic ) doesnt support html shortcode and i am forced to use link

i have searched s2member and got this link

which teaches you how to turn shortcode into links

now, problem is, when i click on the button, it goes to paypal and say its not properly encrypted and hence not working.

if i disable the s2member encryption, it will works but its not secured, user can generate a USD1 pricing to hack the subscription.

i used another method as i search google which suggests people to generate the extermely long length of encypted code and put in the plugin, it worked, but issue it, i figured it wont communicate with my website for API.

sry its a bit long, but i am desperated for a solution