You’ll see the “at capacity” error when ChatGPT servers are extremely busy, limiting access to the service until there are fewer user requests. You can connect to a VPN server in a different location and access ChatGPT to see if this fixes the error — a fresh ChatGPT session and location could allow you access.
However, sometimes you just have to wait. If ChatGPT’s servers are at capacity or down for maintenance, it could be a couple of hours before you can regain access to your account.
ChatGPT also has a premium “Plus” subscription available that enables access even at peak traffic times, but there is no official app available. Don’t be tempted to download and pay for apps that promise you quicker access to ChatGPT. Unofficial subscription apps have flooded app stores, often with price plans more expensive than ChatGPT Plus — these are a scam and should not be downloaded.