Hi!
I have a network 192.168.0.0/24 and i created a dhcp server with pool 192.168.0.20-192.168.0.250
But, i want to set specific IP for example 192.168.0.6 to specific MAC.
First, i go in dhcp-> leases and set make static in specific device (for example this device get 192.168.0.21).
When i change ip after set make static, the status from device is "waiting" and i can't ping the device from de new ip.

What i'm doing wrong?

release/renew ip on client

Or reboot the client. Or disconnect the LAN cable to the client and then re-connect it. Or wait a while.

Changing the IP to static or changing that IP address on the server does NOT force an immediate IP change on the client. The IP will change next time the client requests an address.