I cant see my brother's Minecraft LAN world anymore, I used to be able to see it but cant anymore, please help

I used to be able to see the LAN world but today when we decided to play together, I couldn’t see it anymore and it would say failed authentucation servers are down or something like that, ive tried direct connect, it didnt work, I’ve tried allowing Java to access firewall, it still didnt help, Please help.