I am using a Raspberry Pi 3 A+ with Raspbian Stretch (updated/upgraded about a month ago), connected to a Manga Screen 2: http://wiki.thing-printer.com/index.php?title=Manga_Screen_2
I have used this Raspberry Pi with a 1920x1080 desktop monitor, and also with an 800x480 5" HDMI touchscreen, and it works flawlessly with both of those. I am able to get the screen to display correctly on the Manga Screen 2, and the touches register correctly, but after setting config.txt and making a .rules file the wifi is magically disabled and I am out of ideas.
My config.txt is unmodified except for the hdmi configuration that the wiki for this screen specifies. wpa_supplicant contains the correct information, since it is unchanged and was working with a different screen just a few hours ago.
When I scan for wireless networks with iwlist wlan0 scan, I am able to see all the ones I should, including the one it was connected to before I switched screens. However, hovering over the wifi icon shows "wlan0 not associated" and ifup wlan0 tells me "unknown interface wlan0."
This fix did nothing: RasPi 3 - wlan0 not associated
I have tried 4 different Raspberry Pi 3 A+'s, as well as 3 different power supplies, and nothing has made a difference yet.
Any thoughts are appreciated. Thanks.
Edit 1: I believe the problem is caused by this line in config.txt:
hdmi_timings=1080 1 100 10 60 1920 1 4 2 4 0 0 0 60 0 144000000 3
When I comment out my changes to config.txt and connect the pi to an external monitor, the wifi connects with absolutely no issue. I need to read more about what that line actually does.