If a user receives error [Citrix Receiver cannot write connection file /Users/<username>/Library/Application Support/Citrix Receiver/Module], the installer has created a read-only file which needs to be deleted.
Open a Finder window, and navigate to the Citrix Receiver directory under the user’s application support library. You should see a file named [Module]. (to access the Library folder, open Finder and select “Go” from the top option and select folder. Then type ~/Library. You can then select Application support.
Move the [Module] file to the trash, and try to connect again.