I’m not sure what the original question here is asking, I’m guessing you are seeing some error messages when trying to run g16. It would be helpful to include more examples, such as the command(s) executed, your operating system, and other tangible items.
I’m assuming the second item is answering the first, and this may be misleading to other users.
By default, Gaussian should set itself up with the correct permissions as part of the installation process, whether it is a binary install or an installation built from source code. Gaussian is usually pretty clear in their installation instructions
In general, all users of Gaussian on a Linux system should be members of a linux group associated only with Gaussian. For example, a group named g16. Then only the group permissions should be enabled, with world permissions turned off.
If you are encountering any permission issues with Gaussian, you should check with whoever installed it to make sure they set the permissions according to Gaussian’s instructions.