no access to mikrotik clients within the same lan network...help me!

Hi everyone
I currently have a mikrotik client with firmware 6.40 running without any problem
but in this month of January I installed 4 new clients and I detected that I cannot access those client computers from the same lan
so I can not see the performance of the service to my other client computers if I can enter update to the most current version of mikrotik and also does not let me see that it may be the problem.
Something happened to you?

Hey. Do you have an ARP records of these hosts? After you pinged them.

yes