Start where the problem begins
If the homepage does not load, check another ordinary website and reload once. If only an old bookmark fails, search from Home rather than repeatedly opening the same broken address.
If the page loads but a title is missing, remove restrictive filters and add the production year. Check whether you selected movies when looking for a series. Alternate titles may also explain a mismatch.
When Watch now is the problem
Confirm the viewing country on the title page. The link should open a JustWatch search for that title. A service available in one country may not appear in another. An empty listing does not prove a worldwide outage.
When playback is the problem
If the destination player opens but stops, try its reload or quality controls. Check whether other titles on that service behave the same way. A single problematic edition calls for different help than every page failing on your connection.
Keep the error text, device, browser and title name together. Avoid clearing your entire browser as a first step, because it can remove saved information. Back up your list before changing storage settings.