Just to confirm, the Dorico Application IS in my Applications folder. I am the only user on my machine and have Permissions to Read & Write for these installers. I have VIPro, VEPro, MIR Pro, Synchron player ....I've been using VSL since 2001 and have installed many pieces of software and updates over the years, including updating the Vienna Assistant on my Laptop via an Installer Package, just today! This is the first time I have encountered this, and I can only assume that there is something wrong with the installer.
I can open the installer with 'The Unarchiver' on my Mac and I get a folder full of the individual packages - I have Permissions for all these individual packages. When I double click on one I get a message to say that the package is damaged.
I have today tried to install the same package on my Laptop which is a similar system to my main Mac Studio. Both are on Mac OS 12.6. Exactly the same thing happens. @Stamak is experiencing the same thing (see above) and he is on an even older OS (11.7) so maybe that is something that is causing a problem. I will consider upgrading my OS.
Best wishes, Andy