I have MacBook Pro (Late 2013) and a router, that serves two wireless network (2.4GHz and 5GHz) with different names. Most of my devices are connected to 2.4GHz network, while some are connected to 5GHz network. I'm running on OS X El Capitan 10.11.6.
After MacBook goes to sleep or gets rebooted it couldn't find ANY of my networks, while it could see a number of neighbour's networks. After some time it suddenly finds both of them and connects to 5GHz.
I've tried everything, removed network configuration from /Library/Preferences/SystemConfiguration/, created new location, turned wifi on and off, you name it. Nothing works, as soon as it goes to sleep it looses my networks.
My other devices could see both my networks perfectly at all times.
Scan utility from Wireless Diagnostic is unable to detect any of my networks as well. Actually running wireless diagnostic doesn't yield any results, because it also couldn't find my network.
This started as soon as I bought new router, but I did have different problems with my old ones and this same MacBook. Seeing as my other devices work just fine, I assume router is not to blame. Anyway I could post my network settings if it's somehow relevant.
Reinstalling OS X is not an option, since 1) it's not an actual solution and 2) this is corporate MacBook.
Best Answer
Yesterday I've played with the router a bit (even though I thought it's not to blame) and figured that my country code (transferred via 802.11d) was set to
TW(factory default I guess). And almost every other network hasRUcountry code. So I've changed my router's country code toRU(lost couple of channels and ability to serve 802.11ac) and after that I haven't experienced any problems with connection (yet).I think (not 100% sure though) that my other devices just ignore country code or don't use 802.11d protocol at all. And that's why only MacBook was affected.