Error code 280 means the Roblox client on your device is out of date and no longer matches the version the game servers expect. Roblox updates often, and once a new version rolls out, older clients are turned away until they update.
If a fresh install still shows 280, the new version may still be rolling out to your region, so wait a short while and try again. If it persists for hours after a clean reinstall, check Roblox server status, since a bad rollout can leave some clients unable to match the servers.
Why does error 280 appear out of nowhere? Roblox pushes updates regularly, and a client that was fine yesterday can be out of date today once the servers move to the new version. The fix is simply to update.
Does error 280 mean my device is too old? Not usually. It means the installed copy is outdated, not that the device is unsupported. Updating or reinstalling normally fixes it on the same device.
Can a wrong date and time really cause error 280? Yes. Update checks and secure connections rely on the system clock, and a clock that is far off can block them. Setting the time to automatic is a quick check worth doing.