Is 9anime down?
The site is a set of pages served from one address, and it is rarely the part that fails. If it will not load, try it over mobile data instead of Wi-Fi, or the reverse; if it loads on one and not the other, the network you were on is filtering it, which schools, offices and hotels do to every streaming site. If it loads on neither, wait a few minutes; a brief outage at the host is the only real "down", and it passes. Most "9anime down today" searches come from people using a copy on another suffix, or remembering the AniWave closure; the address page has the one to keep and the what happened page has the history.
Bad gateway, server status, servers
"9anime bad gateway" and "9anime servers" are phrases from the old site's video hosts. Here the pages are static and the video plays on the service you open with Watch now, so a bad-gateway message belongs to that service's player; reload it, or pick another service from the list.
The page loads but looks wrong
Near-black background missing, posters blank, menu in a column: 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 finds nothing
Search runs on JavaScript; with scripts blocked the page stops at "Loading results", so allow them for this site. Search runs but finds nothing: try the romaji title or the English one, drop a filter, check the season number against the way the cours are counted, or switch Type to All. The search guide has the rest.
Watch now is empty, subtitles not working
Watch now lists the services carrying the anime in the country you chose, and the list differs by country and by week; change the country menu above the button. Subtitles and dubs are set in the service's player, one press away; the sub and dub page covers the menu.
Login problem
There is nothing to log into. My List, your country and your episode marks are stored in your browser, with no account; a "login problem" on a page carrying the name is a copy asking for something this site never asks for.
My List is gone
The list lives in the browser that made it. Cleared data, a private window or a different browser and it is not there. Export before clearing; Import restores.