MikroTik

Hi all!
I have a problem with winbox. Some mikrotiks on my network doesn't appear on winbox discovery panel but:
1.they appear on the dude
2.i can ping their ips
3.if i write the ip on winbox they open.
Where is the problem?
I tried to change computer but is the same.
Thank you.

thank you for your reply.
I find the problem: i have one of my links made with ubiquiti airmax; i tried to turn off it and "magically" the routerboards that weren't on winbox list appear!!!