This problem doesn’t happen always, I had a couple of successful sign ups but today I had one that didn’t go through (I found out because PayPal also sends me an email on each signup).
I tried to download the server-scanner but it’s unavailable, I click on the download link and nothing happens.
Below is the (partially redacted) log entry for the IPN from PayPal that wasn’t processed:
LOG ENTRY: Fri Dec 11th, 2020 @ precisely 10:43 am UTC
PHP v7.4.13 :: WordPress v5.6 :: s2Member v200301 :: s2Member Pro v200301
Memory 5.42 MB :: Real Memory 2.00 MB :: Peak Memory 5.44 MB :: Real Peak Memory 2.00 MB
Redacted.com/?s2member_paypal_notify=1
User-Agent: PayPal IPN ( https://www.paypal.com/ipn )
Array
(
[s2member_log] => Array
(
[0] => Unable to verify $_POST vars. This is most likely related to an invalid configuration of s2Member, or a problem with server compatibility.
[1] => Please see this KB article: `http://www.s2member.com/kb/server-scanner/`. We suggest that you run the s2Member Server Scanner.
[2] => array (
's2member_paypal_notify' => '1',
'txn_type' => 'subscr_signup',
'subscr_id' => 'I-REDACTED',
'last_name' => 'Redacted',
'option_selection1' => 'redacted.com',
'option_selection2' => '55.55.55.55',
'residence_country' => 'RD',
'mc_currency' => 'USD',
'item_name' => 'Redacted',
'business' => 'redacted@redacted.com',
'amount3' => 'redacted.redacted',
'recurring' => '1',
'verify_sign' => 'redactedlongstring',
'payer_status' => 'verified',
'payer_email' => 'redacted@redacted.redacted',
'first_name' => 'Redacted',
'receiver_email' => 'redacted@redacted.com',
'payer_id' => 'REDACTED',
'option_name1' => 'Originating Domain',
'invoice' => 'redacted~55.55.55.55',
'option_name2' => 'Customer IP Address',
'reattempt' => '1',
'item_number' => '2',
'subscr_date' => '02:42:54 Dec 11, 2020 PST',
'custom' => 'redacted.com',
'charset' => 'windows-1252',
'notify_version' => '3.9',
'period3' => '1 Y',
'mc_amount3' => 'redacted.redacted',
'ipn_track_id' => 'redacted',
)
)
)
Almost all subscriptions are processed correctly, but since this happened, I felt it could be convenient to have this post since the last Wordpress Update 5.6 gives us that error on the health check.
I’ll keep you all posted if this happens again. I wonder if we still can download that server-scanner or if it’s discontinued.
Thanks again 
