It’s basically a method of verifying the call originated from the number shown in the caller id. The scammers and spammers using voip phones often spoof their caller id to appear legitimate. In doing so they fail that verification. Like I mentioned, sometimes there are false positives, but you can always add the number to your contacts to let the call through. https://www.fcc.gov/call-authentication

I can’t help you with caller id, but Silence has several options for call blocking. I have it set to only allow calls from contacts and calls passing stir/shaken verification. Occasionally calls from businesses that use a single outward facing number will get blocked.

I didn’t take a key, but thanks for the giveaway! You’re awesome!