Can you ping the IP of the phone? If no, sort out the network then try again.
Note that unless you have the Insomnia app installed, the phone will tear down the wifi connection within 10 seconds of the device sleeping.
If you can ping the phone, have you tried to ssh into it? Are you ever prompted to accept its encryption key?
For reference, when asking for assistance, it's helpful to indicate what steps you've already taken to troubleshoot and whatnot.