Mac – How to trigger Appstore check for app updates manually

It appears that some updates have others as prerequisites, and will not show up as available until the others are installed. Thus, Software Update makes a list of all eligible updates, then runs. If a subsequent update was also pending that was not eligible to be downloaded because its prerequisite has not not yet been installed, that update would not make the list. The subsequent check, however, would see if any new updates had been unlocked by the updates installed.

The issue is that the firewall option stops connections from outside to the app but for an update the app initiates the contact to the suppliers server so the firewall does not help here.

the program Little Snitch does allow you to control the app starting a conversation with another IP address and so can do what you want.