Long story short, after a lot of troubleshooting I found out that if you have your home wifi set to channel 13 it doesn’t show up in the wireless adapter UI. Changing it to a different channel will fix it.
But maybe that should be fixed so it shows up regardless of channel chosen.
Issue found on RPi2 with TP-LINK TL-WN722N (this same adapter can see the network on channel 13 if I plug it in a laptop).
I guess it depends on the regulatory country that you have configured for the adatper. E.g. channels 12&13 are not allowed in the USA so if the driver is set to US they would not be available
Yes I’m not from the US and channel 13 is an option on my FritzBox router. And i chose it exactly because it’s almost always clear.
I thought that the country code limitation only applied to broadcasting. Because all my other devices see my network and can connect to it normally.
This is normally an autodetect process based on the broadcasting. Post your dmesg | paste-log and we can check or take a look yourself, you should have something like
cfg80211: Regulatory domain changed to country: DE
Ok, here it is.
I think it’s setting the country code to China?
Anyway. If this is expected behaviour, I don’t want to waste your time. I’m fine having my wifi at a more normal channel 10. It’s not a big deal. 
Maybe have a look here YobiWiki
Based on that you could try:
Add REGDOMAIN=<2-digit code of your country> to /etc/default/crda
or install wireless-tools sudo apt-get install iw and then execute iw reg set <2-digit code of your country>