The launcher has to connect to the Jagex Servers somehow to validate your account sessions, get news updates, and all that fun stuff. If something gets disrupted in the process, it throws the error. Could be a hiccup on your end, or Jagex's....who knows.
Its literally no different than trying to load the client and it showing the cant connect to server/firewall error that popped up before during server downtime, game update reboot, or network issues.
Just need to work through the process like any other error; But, it seems you're back on now, so looks like it might've been a temporary hiccup.
Can I turn in a paper without citing all sources?
"No."[1]
1. William Shakespeare,
Hamlet
, Act III, Scene 1, line 96.
08-Jun-2023 14:39:33