I'm not familiar with those VSTi's but I have had situations where I had to simply move a .dll to a different folder in order for Cubase to see it in the VST instruments list. Usually not just 'move' at 1st, but copy & paste the .dll to one or more folder locations until finding the right one. If you have more than one version of Cubase, maybe the .dll got installed in the wrong folder..? Still, moving .dll's had solved it for me... more than a few times.
* Shoot Between The Eyes!!! * Go US Navy Seals!!!* Team America "K" Yeah!!! *