Aaron has an iPhone 7 and when he has to search for a website, there's a CAPTCHA challenge, but when he types it in, it doesn't do anything at all. He says it never happens on Wi-Fi, just on cellular. Leo says that could indicate that his carrier is sending him the CAPTCHA and it could be broken on their end. Google has a tech note called Unusual Traffic from your Computer Network and it talks about this similar error. The CAPTCHA is there to be sure there isn't a robot running the search.
Leo suggests that Aaron call T-Mobile support about it because Leo has a hunch it's on their end. He should also make sure his iPhone is up to date. Google also wants to block automated searches, and T-Mobile may be the culprit doing them.