I have the same issue.
Strobe2 does not show up in Logic 10.4 as an AU plugin. Previously, I did not have this problem, but I did full reboot of my Mac and updated to Logic 10.4. Since then, Strobe2 doesn't show up in Logic.
What I've tried:
I've checked that the Strobe2 component file is in Audio/Plug-Ins/Component files. The file is there. I've tried deleting the file and replacing, re-running logic, etc. I've also tried clearing the audio unit cache, which refreshed other plugins(Roli) but still did not find Strobe2. I had just re-installed Strobe2 and Logic right before this issue started.
Please help! I want to purchase the new Bass package, but won't purchase until I can load Strobe2 in Logic and Mainstage.