I’ve searched online (in THIS forum and elsewhere) for this issue, and when reading results, either the user hasn’t implemented it properly, or someone from support had requested logs (so I can’t see a solution). I have s2Member Pro. I have a https:// domain. I have the correct IPN inputted into my PayPal account (originally I had a Zapier IPN which allowed me to have multiple IPNs - the one for the other device worked fine, but I hadn’t yet tested the s2Member one… but for the basis of this test, I have put the s2Member IPN in on its own). I have created a button in the s2Member module and pasted the shortcode into my page. I have successfully made a payment on PayPal using a credit card, but on the final screen where it has a button to ‘return to Merchant website’ every time I get the s2member ERROR: Unable to verify $_SERVER[“HTTP_HOST”] error - please check the ‘custom’ value (which has my correct domain, but not the ‘http://’). This is auto-generated by s2member, so I’m not sure why it’s telling me it’s wrong. The payment is successfully taken, but no user account is created on the website. Can you help please? Many thanks 
Andy
S2member ERROR: Unable to verify $_SERVER["HTTP_HOST"]
I’m still investigating…
In the gateway-core-rtn.log there is a line: ‘[custom] => undefined’ - is this this ‘custom’ that the error message is referring to?
I’ve run the s2-server-scanner.php (found on another thread) but the only issue I get is the ‘MySQL Database Extension’ error which I understand I can ignore (!).
There are a few threads with this same issue, but I can’t see any of them with any solution…Is that 'cos there ISN’T a solution, or that there’s something so glaringly simple I’ve missed that everyone is waiting for me to find it myself?
Onwards…
Still no luck… tried deleting my PayPal API signature (suggested on a different thread) and requested a new one, tried using the button code without the ‘www’ in the ‘custom’ parameter, adding ‘https://’ in the ‘custom’ parameter, but no joy for anything yet. I don’t understand why it’s telling me to check my button code when the button code is generated by the s2 plugin…
This is the code that s2Member is auto-generating:
[s2Member-PayPal-Button level=“1” ccaps=“ppbtn_newsig” desc=“New signature button” ps=“paypal” lc="" cc=“GBP” dg=“0” ns=“1” custom=“www.mydomainname.com” ta=“0” tp=“0” tt=“D” ra=“0.01” rp=“1” rt=“L” rr=“BN” rrt="" rra=“1” image=“default” output=“button” /]
Any help/suggestions would be most appreciated Cheers!
Try to rebuild the URL that you save in your Paypal account - it may contain wrong info. Also may replace your s2M copy with a fresh downloaded - may be errors in files.
Hi Krum - thanks for the reply… I’ve just this minute set up a different website with similar settings and had success, so you could be right about a corrupt s2Member installation. I will re-install and keep my fingers crossed
Did you ever find a solution ? I just encountered the same.
Hi Berry, I was unable to debug it in this instance, although I was later able to connect successfully on a different website with (what I thought was) a similar set-up.
For this particular website, re-installing s2Member didn’t help… so I had to resort to creating an alternative set-up using different CRM software (I was desperate) and just keeping s2 purely in charge of membership access rather than purchases as well.
I think I fixed it… at least, not seeing the error anymore in log.
Hi! The same problem here. What did you do to solve the issue? Thanks!
To be honest, I can’t remember.