New setup with questions

I am new to this OS and am learning quick.

New RB750P set in bridge mode. I have an WAN in Port 1, Ubiquiti M2-400 in Port 2, Ubiquiti M5-400 in Port 3.

I can’t see anything in Port 3. I enabled the port it still says disabled port.

any ideas here?
screenshot.jpg

You have no link to this port. Check cable etc.