The problem is obvious i think.
I'm using macOS Catalina (new version of macOS). They are announced 32bit apps are won't work anymore and software developers must update their run profile.
Can you guys do it quickly :-/ ? I'm not able to play Don't Starve Together on my MacBook Pro right now
Don't Starve is running OK BTW. Just Don't Starve Together is not running because of 32 bit apps are unsupported.
Steps to Reproduce
Update your macOS to Catalina (currently in beta)
This issue has not been confirmed by a developer yet.