I signed up yesterday for ChatGPT Plus and was able to use ChatGPT4 and ChatGPT3.5 without any issue during the day. I also downloaded the new ios app and was able to use it throughout the day without any issue.
Today, ChatGPT4 is no longer responding to my inquiries on desktop web or ios, but ChatGPT3.5 is working fine on web. On iOS, I get no response but am unable to find a setting to toggle between the 2 engines, so I think it's only looking at GPT4.
Either way, I have no access to ChatGPT4 at this point.