Thanks for the screenshot! It looks correct; I dunno what happened with regard to your other GV number. It is probably a "red herring" as far as this issue is concerned, though, since your other forwarding destinations do work.
The only other thing I can think of, that might have resulted in the missing number situation is, if you accidentally created say, Google Voice account #1, with that GV-issued number, but then ported the folks' POTS number to a different GV account. It is surprisingly easy to make this mistake, since Google allows multiple accounts to be logged into one browser. Anyhow...
Go back to the same settings page, where you took the screenshot. Click the "Groups & Circles" tab. Click the "Edit" button under "All Contacts", and toggle the setting back and forth to "Ring default phones", even if it is already set that way. Click the "Save" button. Edit every other row, and set them to "Ring All Contacts" phones, again, saving every row's settings. If you want to set up a choice for special callers, like not ringing on calls from annoying cousin Wilbur, then you can do that.
Test inbound calling again.