Sign-in problems

Check the address for typos and the password for caps lock.
If you originally signed up with Continue with Google, use that button — the account may not have a password set.
Forgot it? Choose Forgot password? on the sign-in page, enter your address, and open the link we email you in the same browser to set a new password. Reset links work once and expire; request another if yours has.

The password reset link says it's invalid or expired

Links are single-use and time-limited — request a new one from Forgot password? and open the newest email.
The link must be opened in the browser you requested it from (the reset is bound to that browser). On a phone, request it from the phone.
If you signed up with Google there is no password to reset; use Sign in with Google. You can add a password later in Settings › General › Password.

The confirmation email didn't arrive

Look in spam and in any "Promotions" tab.
University mail filters sometimes hold external confirmation links for a few minutes.
Requesting a new sign-up with the same address resends the confirmation.

Third-party cookies or a strict privacy extension can block the OAuth callback. Allow cookies for neutropic.io and the Google accounts domain, or try a private window without extensions.
If your Google account is managed by an institution, its admin may have to allow the Neutropic app.

Signed out unexpectedly

Sessions expire after long inactivity. Signing in again restores everything — chats and artifacts live on your account, not in the browser.

Desktop app: the browser signed me in but the app didn't notice

The browser hands the session back through a neutropic:// link. If nothing happens:

Look for a browser prompt asking to open Neutropic and allow it.
Copy the neutropic://… link the page shows and paste it into the app's sign-in screen, or open it from the address bar.
Make sure only one copy of the app is running.