You got this error message because you tried to use NECO old result checker site, NECO now has a new site for checking results https://results.neco.gov.ng/.
But if after using this pin on their new site and you still get the invalid message, Please contact customer care.

Please contact customer care and present them with the necessary transaction information, after validating your information, your pins will be sent to you immediately.

Contact our customer care, and you will be asked to provide us some necessary information to identify that you really made that transaction, if successful, you will be sent your transaction ID to either your email address or your phone.

Sometimes due to network connection problems, emails containing your pins may fail to deliver but you can also get your pins by Tracking your Transaction using your transaction ID that looks like this ECM-10007805650. Any other issue please contact our customer care.