Which part stopped working?
A page that will not open, a search with no results and a video that stops halfway through are different problems. Read the exact message and note where it appears. If you have already left Catflix for a viewing option, that service controls the video.
The page is blank or unfinished
Reload once and wait for the page to settle. Test another Catflix page in the same tab. If text appears but pictures do not, the image connection may be the part that failed. A private window can help compare browser settings, but your saved list will not automatically appear in that separate session.
Search says no titles match
Reset the filters and enter a few distinctive words. Check whether Movies is selected when you meant a series. For a show, search the series name first and then inspect its season list. A character name will not necessarily match a cast member's name.
The movie opens somewhere else and then stops
Check that viewing service's status message, selected quality and connection. Try another available quality before repeatedly refreshing. If the error mentions your country, choose the correct viewing country and inspect the options shown for that location.
Do not clear all browser data as your first step. It can remove Catflix bookmarks stored by the browser and your local list data. Create a list backup before changing storage settings.