Cannot get the Mk 9 trans to lock - help!

Doing some basic maintenance clean-up in the MK9, pushed in reverse and 3-4 lever and the trans WILL NOT LOCK!!! Tried rolling, multiple times engaging...NADA. What am I doing wrong that is probably obvious to everyone but me>>>>help!



One suggestion is the reverse slider was installed incorrectly or fell of...so what next? Impact wrench and look out!!