Apple changed some things regarding WiFi with iOS 13. If you want to use CNCopyCurrentNetworkInfo your app needs to have one of the following
I believe that you match one of the following condition which is suggested by Apple:
1 :Apps with permission to access location
2 :Your app is the currently enabled VPN app
3 :Your app configured the WiFi network the device is currently using via NEHotspotConfiguration
In my case even i have location services enable when was facing the issue.
After some workaround here are i found the two solution which you can try:
1: Reboot the device. This works for me!!.
2: Update the OS if available.
I am not sure it helps you but in few cases it should work, few people suggest reboot 2-3 times work for them.
Another good news from Apple that they fix for this issue on iOS 13.3 beta version