Check for malicious software?

Check for malicious software?

I cannot install various apps on my Mac - Monterey 12.6. 

I get a message that “the app can’t be opened because Apple cannot check it for malicious software.”

I have tried to locate the app in question in my application folder and control click it - and I have tried to click “Open anyway”, but still I get the same dialog box: can’t be opened because Apple cannot check it for malicious software.

The Dropbox team has tried to help me, but it seems to be a macOS problem(?)

I have met this problem with the apps from Adobe CC, Dropbox and Astute Manager, which all have run for years with me, and still run on my other devices. Does anybody have an idea what to do?

Thanks

Michael