Paypal redirect "Not Acceptable!"

Hi, I’ve recently added s2Member Pro to my website ( I tried my first real subscription and everything worked up to the redirect back to my webpage. So I was able to click the generated paypal button and pay for the subscription, but when it tried automatically redirecting me back, it gave this error:
Not Acceptable!
An appropriate representation of the requested resource could not be found on this server. This error was generated by Mod_Security.
I contacted Hostgator support and I think they got me past that part, but now when I try the redirect link, it hangs and doesn’t load. After the page doesn’t load, it eventually says this:

ERROR: Unable to verify $_POST vars.
Please contact Support for assistance.

This is most likely related to an invalid configuration of s2Member, or a problem with server compatibility. If you are the site owner, and you’re absolutely SURE that your configuration is valid, you may want to run some tests on your server, just to be sure $_POST variables are populated, and that your server is able to connect/communicate with your Payment Gateway over an HTTPS connection.

s2Member uses the WP_Http class for remote connections; which will try to use cURL first, and then fall back on the FOPEN method when cURL is not available. On a Windows server, you may have to disable your cURL extension; and instead, set allow_url_fopen = yes in your php.ini file. The cURL extension (usually) does NOT support SSL connections on a Windows server.

Please see [this thread] for details regarding the ideal server configuration for s2Member.

I’ve received two emails from Paypal saying my subscription has gone through, but I don’t know how to register my profile to sign-in to the website now. I don’t get any email from s2Member.

Here’s the button link I use:
[s2Member-PayPal-Button level=“1” ccaps="" desc=“Guild Member / $25 USD per year for full member access ($15 for first year)” ps=“paypal” lc="" cc=“USD” dg=“0” ns=“1” custom=“” ta=“15.00” tp=“1” tt=“Y” ra=“25.00” rp=“1” rt=“Y” rr=“1” rrt="" rra=“1” image=“default” output=“button” /]

I can also share the long redirect URL if it’s helpful. I’m trying to open up these subscriptions to the public in just over a week so I need to somehow understand how to fix this.

Does anyone know if I need to do anything server side to fix this or if there’s a simple way to generate the registration email for new subscribers?

Best regards,

It appears as though it’s working now. I think after my hosting company helped me fix the first issue, it works when starting a new purchase from scratch.

Hope this helps someone else in the future.

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Thanks for the update, Mike. i’m glad you sorted it out.

For future reference if someone finds this thread through google, see also: