CI+GoCart: Form submission works in localhost but NOT on live server

UPDATE: The solution to this problem was not changing any code. Instead, I realized that Dreamhost shared hosting was forcing www. before all URLs. I disabled this so only http:// would work (www. is redirected to http:// now), and the code all started to work.

Thank you so much for this solution it worked for me too.
To check this solution I just inspect my form and remove <www> from my action form URL then submit the form. i do print_r() and i got all post data. again thank you so much for this solution, I was stuck with this issue in fact I was not able to get the search key that is why I was getting the different info on the web.
Finally, my issue has been resolved.

eg. I am working with Codeigniter 4
Not Working
action="http://www.test.com/test-save"

Working
action="http://test.com/test-save"