I can't connect to multiplayer mode.

When I try to connect to multiplayer mode, I’m asked to authenticate again, even though I’ve already authenticated many times. Please help me, Mojang. I want to play multiplayer and enjoy Minecraft with my friends, but I keep running into obstacles like this. Please fix this bug because it’s very frustrating. I can’t play multiplayer at all. When I try to connect to multiplayer, I’m told to check with my guardian and authenticate. Even after I authenticate, I still can’t play in multiplayer mode. Please help, Mojang, because this is really frustrating.