limited or no connectivity problem

Hay,
I have a problem that some time many clients get error “limited or no connectivity” and they cant get IP from server while there is availbale IPs in DHCP pool rule
I use 10.0.0.0/23
Some times its solved by restart server
What is the problem or what i have to do to avoide these issue?
If i but the lease time 1day is these better ?Is there any problem may be happen if i do that?

Thanks

what version do you use? what is shown in RouterOS log?

i use 3.13

Nothing becuase i make it 100 line only,How i can save all log and send to email or safe to file so i check for all log issue

100 lines is quite enough to see errors in real time. just use ‘Fix network connection’ menu item on client and see what ROS says