I downloaded DeltaChat on OSX 10.15 Catalina.
During start, OSX complains that it cannit start DeltaChat because OSX cannot check the application.
(OSX Catalina only allows appliactions from the store or those verified by Apple)
We sign it with the key we get from apple so this is strange, can you provide more info? which desktop version? a screenshot of the error could help too.
Ok I found a solution or maybe a workaround
In Systemeinstellung > Security “Apps-Download erlauben von” App Store und verifizierte Entwickler" was already enabled. But now beside this Menu there was a message “DeltaChat ist blockiert, dennoch öffnen?”.
I confirmed andit started.