Minecraft won't detect to LAN server?

My 3 friends and I have been trying to connect to a server together for months. They made one and were all able to connect but my computer wouldn't even detect any servers at all and we thought it was because my Minecraft was pirated. I bought the actual version and we're all connected to the same router via ethernet cables but my computer still won't detect anything. Is there a setting I should know about or something?

Ok whoever is in control of the server panel needs to make acces available for all guests, and also add everybody to the operator list, and also add the names to the whitelisted list. I would recommend using serverminer.com and pay those to set up a server for you instead

Besides access rights, you need to make sure your Java versions are all the same as the server, as well as the Minecraft version must be the same as well.

The LAN server "detection" is only for minecraft on another client that has enabled "Open to LAN".

For a regular minecraft server you need to add the LAN IP of the server to your server list (or IP: port if different than default port 25565). Then you should be able to connect to it like any other server, assuming that you are whitelisted on the server if that is enabled.