ZeroTwo's apps do not show an account alert called "Suspicious Activity". The nearest thing is a message on the web sign-in page: "Unusual activity detected. Please use email login with CAPTCHA verification." It comes from an automatic check on how the sign-in page is being used. It is not a report that something happened to your account.
When it appears
On the web sign-in page, choosing Continue with Google, Continue with Apple or Continue with Microsoft first runs a check in your browser. The check looks for signs that the browser is being driven by automation software, and for signs in how the page is used, such as a click within a second of the page opening, no pointer movement or unusually fast typing. ZeroTwo stops the sign-in and shows the message only when the browser reports signs of automation and at least one other warning sign is present too.
Signing in with an email address or a phone number does not run this check. Those use a CAPTCHA check instead (see When does ZeroTwo ask me to complete a CAPTCHA?).
What to do
- Use an ordinary browser window that is not started by a testing or automation tool. The check is looking for that kind of browser, and it can stop the sign-in even when you are the one using it.
- Sign in by email instead. On the sign-in page, type your address in Email address (if the phone fields are open, choose Continue with email first), complete the CAPTCHA that appears and select Continue. ZeroTwo emails you a sign-in link, and its "Check your email" screen says the link will expire in 1 hour.
Protect your account
On the web and in the desktop app, open Settings > Security. The iPhone, iPad and Android apps have a Security screen with the same two-factor authentication switch and the same log-out options.
- Two-factor authentication. Switch on Two-factor authentication and scan the QR code with an authenticator app. Once it is on, signing in asks for a six-digit code from the app.
- Backup codes. A Backup codes row appears on the web once two-factor authentication is on, but the sign-in prompt only accepts the authenticator app's code, so do not rely on backup codes to get back in. How do I turn two-factor authentication on or off in ZeroTwo? explains why.
- Log out. Log out of this device has a Log out button that ends the session you are using. Log out of all devices ends every session, including this one, and other devices can take up to 30 minutes to be signed out.