Original Launcher is acting like a Pirate Launcher

My launcher have the default Original Launher's graphics. 

I've purchased Minecraft on https://minecraft.net/pt-pt/ with a cost of 23,95 €. But when I try entering a server like Hypixel (mc.hypixel.net) and VentureLand (mc.ventureland.net), it says "Failed to login: Invalid session (try restarting your game)". But when I try entering a server like Jartex Network (play.jartexnetwork.com), it never shows this message. My friend have Pirate Minecraft, and he telled me: "Hey Gamer_top_13, Hypixel only supports original Minecraft, I cannot play with you." And I think Jartex Network supports Original and Pirate Minecraft. And I'm using a server host to my server on Minehut, and it have a lobby for all players, to enter other hosted servers with a menu. I've tried to enter a server that I don't remember IP, and it instantly automatic perm-banned me with this reason: "alt abuse". My nickname on Minecraft is Gamer_top_13. But it appears with other friend. He got the same problem. But sometimes, it don't shows the message and I enter server normally. Sometimes it bugs, other times it don't bugs. It's the most strange thing, it showing and when I try restarting my game, it can show or don't show the bug message. I don't show evidences because I'm trying to execute the bug and it don't happens, as I've specified in the 2nd bold text.

How to reproduce bug:

1. Launch Minecraft
2. Try entering a server like mc.hypixel.net or mc.ventureland.net (in the most cases with other players, it works normally, the bug can be caused by latest downloaded Minecraft's, I play Minecraft since march 2018 and it bugs)
3. The bug have chance of happening and not happening, to fix don't spam trying to enter server, it happens, try restarting your game and it can appear again or don't appear.