Troubleshooting

See what the tracker does

Add debug: true to sublim.o (or to init()), reload, and open the browser console:

JavaScript

sublim.o = { projectId: 'YOUR_PROJECT_ID', debug: true };

In the Network tab, requests to tracker.sublimanalytics.com/api/v2/events should answer 202.

You're testing on localhost. The tracker stays off there and logs Sublim: Tracking disabled on localhost. Add trackLocalhost: true in development, or test on the live site.
The snippet isn't on the page. View the page source and look for cdn.sublimanalytics.com/loader.js. On a single-page app, check that it is in the shared layout, not on a single route.
Wrong project ID. The request answers 400 with unknown project. Copy the snippet again from Settings → Installation.
The request answers 403 domain not allowed. Your project's domain protection doesn't include this domain: add it in the project's technical settings.
Your IP, path or country is excluded in the project settings, or the visit comes from a bot or a headless browser.
An ad blocker or a strict CSP blocks the script. Check the console, and allow the CDN origins.

sublim('trackEvent', …) called after the tracker has loaded is never sent. Use sublim.trackEvent(…), or the helper that handles both cases.
sublim.trackEvent is not a function means the call ran before the tracker loaded. Use the same helper.
The name is case-sensitive: Lead and lead are different events.
On localhost, see above.

Properties must be inside props: sublim.trackEvent('x', { props: { plan: 'pro' } }), not sublim.trackEvent('x', { plan: 'pro' }).
Nested objects and arrays are stored as text. Send flat values.

trackEvent's revenue.currency defaults to USD, while trackPurchase and automatic detection default to EUR. Always pass currency.

The form needs an email or a phone field. See what counts as a lead form.
A field whose name looks sensitive (password, token, card number…) excludes the whole form. Matching is loose: pin also matches names such as shipping_address.
For forms the tracker can't see, send your own lead event and switch the leads source to it. See Leads look wrong?.