From facebool cubase user group:
CUBASE 9 DOESN’T SUPPORT 32bit VST’s anymore???
HAHA!!! YES IT DOES!!! 
- just like 8.5, with a little trick!
As a big Cubase-fan I was very disappointed that they removed it’s compatibility for 32bit-Vst’s. After researching I got the following solution:
In the Cubase-program-folder you find the folder “components”.
The TRICK is just to copy (and replace) the following 2 files from Cubase 8.5-components-folder to the one in Cubase 9:
“VstBridgeApp.exe”
“VstPlugManager.dll”
(please don’t forget to backup the C9 components folder first)
After that let Cubase 9 rescan your PlugIns - maybe it helps to delete the blacklist-files in the Roaming-folder first.
With this little trick I’m using my Cubase 9 just the way I used 8 all the time, all the 32bit-PlugIns are now present in Cubase 9!
I don’t know how it works with mac, I guess there should be a similar way to get it working there 
Have a nice day
This is the solution for old steinberg plugs that won’t run in jbridge! At least for now.