>>It's possible you accidentally blocked it once and it's in your list. You might check that and put it in the allow list instead. Or uninstall completely and reinstall comodo and make sure you allow the first time you are prompted. Is it remembering what you allow? It sounds like you have the version that had that bug in it.
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>What is your version and if you define a trusted application, is there a way to see the list of what you defined? When I go to this dialog, I can select and apply, but I don't see how the changes apply.
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>My version is 3.13.

I just checked and if you look under Settings, Manage My Configurations, I only have Optimum Security marked as active.
Under Defense, my trusted software vendors, I have Microsoft listed 3 times.
Under Defense, Advance, My Security Level is "Clean PC" and I have Trust the applications digitally signed by trusted software vendors checked, but nothing else is checked. On the monitor settings tab of the same window, everything is checked.
Under Firewall, Define a new trusted application, I added VS long ago. I have a network zone defined for my local network.
Do you have anything under "My Pending Files?" If anything is sitting there, Comodo will continue to prompt to block until a decision is made.