A issue with joining multiplayer severs, such as - "hypixel.net" or "bedwarsclubpractice"

When I try to join those servers, this message pops on my screen.
I bought Minecraft yesterday, and I hoped that everything would work clear, but it didn't.
I can join to offline multiplayer servers only, as they don't require premium account, which I have.
But, when I am trying to join servers which require premium accounts, I cannot do it, as explained above.
I need help with that ASAP, thanks.