Check for Device UID/Serial number for access to website

So I have got it roughly working if I use a browser, but the app still doesnt work, it reports the below error: TCL error: /Common/TMCertCheck - while executing "X509::subject $cert" The rule I am using is: get certificate data when CLIENTSSL_CLIENTCERT priority 1 { set cert [SSL::cert 0] set subject [X509::subject $cert] set issuer [X509::issuer $cert] set version [X509::version $cert] set clientIP [IP::client_addr] check Certificate common name to see if it contains the FQDN for Virtual server if { $subject contains "CN=MyEmailAddress" } { uncomment the line below to validate that the iRule is accepting a valid certificate log local0. "cert CN valid" } else { if the certificate is not valid log client IP and reject connection log $clientIP log local0. "cert CN not valid" reject } }