You have to download the right version of the custom codec. If you are using the MX Player v1.9.17, then open the google drive link on the custom codec thread & download the version 1.9.8. If you have downloaded from the second link, then that's for MX Player 126.96.36.199 and newer.
Kindly think about adding version number to the zip file name as well. it will reduce the confusion. all your package names are same for every new version. so, user may get confused.