Check that your install works

The Setup page

Settings → Projects → your project → Setup lists the Sequential SDK and session replay always. Each reads "no events yet" until its first event arrives. Another source (PostHog, Mixpanel, Amplitude, Pendo, Smartlook) shows only from its first event, as "receiving". While a source is not shown, a line under the list says "Other sources you install show here after their first event." The page checks again every few seconds. Events are written in batches, so allow up to about a minute. Session replay can take up to about 7 minutes to show "receiving". The page checks for 5 minutes, so reload it if the line has not changed.

In the browser

Open the site in a normal browser, open developer tools → Network, and filter by the Sequential API host.

You see	It means
200 / 204	Accepted.
401 unknown_ingest_key	The key is wrong, revoked, or belongs to another source. A PostHog key only works with PostHog, a replay key only with the recorder, and so on.
403 Bot traffic not allowed	The request looked automated: a headless browser, curl, a server-side SDK. Test in a normal browser.
403 replay disabled for tenant	Session replay is switched off for the project.
413	The request was too large: over 1 MB for most event requests, or over the per-session replay size.
429 with Retry-After	The project went over a rate limit: 20,000 events a minute, or the replay upload limit. The Sequential SDK and the recorder wait, then send again. See Limits.
Blocked, no status	The page’s Content-Security-Policy refused it. See the CSP section of the SDK’s page.

Session replay: window.__lxReplaySessionId in the console shows the current recording’s session id. window.__lxReplayFlush() sends what is buffered now instead of waiting.

Things that look broken but are not

• Nothing is recorded for a visit shorter than the project’s minimum replay duration (2 s by default; the project’s own value is under Settings → Projects → your project → Session replay).
• A project’s sampling setting can skip a session on purpose. New non-production projects record 10 % of sessions.
• PostHog feature flags evaluate as off. Sequential does not serve flags.
• Automated end-to-end tests do not show up. Sequential rejects headless browsers as bots, and posthog-js itself drops events when it detects automation (navigator.webdriver, a HeadlessChrome brand), before anything is sent.