It will not load
Switch the phone from Wi-Fi to data, or the reverse. Loads on one and not the other: the network is filtering it, which schools, offices and hotels do to every streaming site, and data or a trusted VPN is the way through. Loads on neither: wait a few minutes; a short outage at the host is the only real "down", and it passes. Most "578movie down" searches come from copies on other suffixes, which do go down for good; the address page has the one to keep.
It loads but looks wrong
Charcoal background missing, posters blank, menu in a column down the left: the stylesheet did not arrive. Reload once. Still wrong: the browser is holding an old copy from before an update; clear the site's data and load again, or on a phone close the tab and reopen from the icon.
Search gives nothing
Search runs on JavaScript. Scripts blocked, and the page stops at "Loading results"; allow them for this site. Search runs but finds nothing: drop a filter, widen the year, try the English release title or the original one, switch Type to All. The search guide has the rest.
Watch now is empty
It lists the services carrying the title in the country you chose, and the list differs by country and by week. Change the country menu above the button. Nothing there yet: add the title to My List and look again next week; titles move between services constantly.
Video stutters
That is the service's player. Close other tabs and apps, drop the quality a step, reload the player, restart the TV app. HD needs about five megabits a second; below that, buffering. The quality page has the numbers.
My List is gone
The list, the country and the marks live in the browser that made them. Cleared data, a private window or a different browser and they are not there. Export before clearing; Import restores.