WIFI cannot connect

[PSFactory]

My friend has a Sony Xperia E. He is unable connect to his home WiFi. The phone finds it but won't connect. It will connect to my phones WiFi hotspot no problem (S3). We tried most of usual solusion (forget network, checking security protocol, double-checking password).
He also restarted his access point.
Can anyone help, please?

 

[Almeuit]

Ensure the DHCP server on his router has enough IP addresses to hand out.

 

[PSFactory]

Yes, we've checked it. Router has 20 IP addresses, but only 7 used.
Additionality, MAC address isn't checking on router.

 

[Gurinder Kaur Pannu]

My friend has a Sony Xperia E. He is unable connect to his home WiFi. The phone finds it but won't connect. It will connect to my phones WiFi hotspot no problem (S3). We tried most of usual solusion (forget network, checking security protocol, double-checking password).
He also restarted his access point.
Can anyone help, please?