Connectors
Agents get services like Notion, Sentry and Cloudflare from your Connectors gateway, and Gmail, Drive and the like from claude.ai's connectors on each login. Now and then one needs signing in again.
The Connectors icon (the plug) near the bottom of the left-hand rail opens a panel listing the gateway's services and whether each is signed in. A blue dot on the icon means one is signed out: click Connect beside it, and its sign-in page opens in your browser. A grey dot means something's off that usually sorts itself out, such as the gateway not answering for a moment. The arrow in the panel checks again, and the ⓘ says more. If the gateway can't be reached at all, the panel says so.
When an agent runs into a service that needs signing in, it asks you in its reply, with a button that opens the page to do it on. claude.ai's own connectors are signed in on claude.ai (Settings > Connectors), on the login the thread runs on.