what this means in my log

failed to get ip address for host 00:60:43:00:42:d6/65.11.740.225: pool empty(6)

[admin@MikroTik] > ip dhcp-server print
Flags: X - disabled, I - invalid
# NAME INTERFACE RELAY ADDRESS-POOL LEASE-TIME ADD-ARP
0 dhcp1 ether1 dhcp_pool1 3d

and what this ip means 65.11.740.225

and when this lines appears , reguest time out to my dns

in short that means: pool empty(6)

longer repply: POOL EMPTY, check ip pool

what do you have in "/ip pool print" ?

[admin@MikroTik] > ip pool print
# NAME RANGES
0 dhcp_pool1 192.168.100.2-192.168.100.254