Hi Don,
There could be multiple areas causing this problem, but usually it's a setting that she's accidently selected or a OS "bug" often cleared by a cold boot, clearing wifi passwords (cache) or restoring wifi setting to factory default.
AP = Access Point = wireless router
I doubt it's the wireless router, but a few thoughts:
1) Via the router's DHCP configuration have you limited the number of connections? The default is usually an entire subnet, but sometimes older routers were limited to 15 or less connections (technically would only issue 15 IP addresses and they would have to time-out). <-- Just an FYI, although a router can support 250+ simultaneous connections, most consumer grade router's performance dies at 3-10
simultaneously used connections. They simply don't have the CPU power to provide encryption, and maintain TCP connections. Even commercial quality (i.e. Cisco) can barely support 25-50 without a noticeable performance impact.
2) Are there many other routers in your area? i.e. when you search for an AP is there more than 3-4 APs all with good signal strength? Normally an AP will search for a channel(s) with the least interference, but some older routers suck at this and you have to set then manually. I use this tool (
https://inssider.en.softonic.com/) for identifying nearby APs, their channel and determine if I have to manually change my APs. <-- 95% of the time on newer APs you are okay, this only applies if you are using an older AP or have manually set the channel.
3) Do you have any weird encryption of signal types manually configured on the AP? Defaults generally work, but make sure G and N are both enabled and WPA2 Personal - AES is enabled.
It's probably the Mac itself:
1) Reboot the mac from completely off.
2) Reboot the AP.
3) Make sure the Mac is fully patched.
4) Clear the network from the Mac and retry: System Preferences >> Network >> Advanced and select your home network to clear, press the (-) and agree to Remove. Then retry connecting
5) Turn off Bluetooth
6) Try the suggestions in this link:
https://support.apple.com/en-ca/HT202222
Is the router provided by your ISP? If yes, try their tech support.
If none of the above works, please post the make/model of the AP and the OS version of the Mac.