What you seeLikely causeFix
Codes like &6 shown as textVanilla servers don’t understand & codesUse § codes, written as §
Strange characters around the colour codesThe file was saved in an encoding that mangled the § signWrite every § as § so the line is plain ASCII
Everything on one lineNo line break escapePut \n between the two lines
The second line is missing or ends earlyA real line break in the file ended the settingKeep the whole MOTD on one line of the file, using \n
Bold or italic disappearsA colour code came after the formatting codeColour first, then formatting: §6§l
Formatting runs into the second lineNothing resets it at the line breakAdd §r before \n
Hex colours look like the wrong colourVanilla only has the 16 standard coloursUse standard colours, or a MOTD plugin
A backslash vanishedA single \ starts an escapeWrite \\
Text is cut offThe line is wider than the server listShorten it and check the preview
The old MOTD still showsThe server wasn’t restarted, a proxy sets its own MOTD, or the server list hasn’t refreshedRestart, check the proxy config, press Refresh in the server list

A line that works

motd=§6§lMy Survival Server§r\n§7Whitelisted, apply on Discord

Build yours in the MOTD Generator to get the escapes right, then paste the whole line over the old one.

See what the server actually sends

After restarting, check the server in Server Status. It shows the MOTD as the server sends it, without your game’s server list cache in the way. If it looks right there but not in game, the problem is the cache or a proxy, not the file.