I upgraded to the most recent os for Mac. OS Catalina.
This is not really the case. macOS Catalina is not the latest version of macOS, Mojave is. Catalina is the upcoming version, now in a stage 3 beta.
You've installed the latest BETA operating system, NOT a final release.
You should never expect production quality experience when using pre-release OS versions, and especially in conjunction with DAWs.
Usually you should wait to get a "green light" from the creators of the software you depend upon, before installing an OS upgrade.
I also tried the Catalina beta, but not on a production machine, and as you experience, not much worked except basic applications. Lots of plugins didn't load, and the system was basically what I'd expect from using a beta; rather useless.
This will get fixed, but until then, you have to follow the system requirements for the software you want to use. In the case of Studio One 4, this is macOS Mojave. Catalina isn't supported officially on any DAW that I'm aware of at this time.
Take Avid's Pro Tools as an example, they just recently got a version up and running on macOS Mojave, and that's almost a year after the first release. Still many Pro Tools users can't upgrade to Mojave because of various DSP issues and whatnot.
You have to have some patience, bro.