Every time I try to play multiplayer servers, it says "This server is not compatible with Minecraft.net".

I logged on to Minecraft and clicked multiplayer. It was suppose to let me join the server and let me play.
When I clicked the server I wanted to play it said " This is not compatible with Minecraft.net". Every server I tried did not work at all. My brother tried to help me fix it but it didn't work. Him and my sister's Minecraft works perfectly fine.
Here's what I did:
1)Log into Minecraft
2)Clicked the"Multiplayer" button
3)Waited for it to log into the server
4) A prompt popped up saying it wasn't compatible

Please help me fix this bug. I don't know if I have to update my Minecraft to 1.9 or not, but I really need help.

~Jade_The_GamerxX
P.S. I need at least 6 hours a day with Minecraft. HURRY!