Yes, changing from auto to channel 6 fixed the problem.
I'm still wondering why I can't use some channels, but that's not really a problem. Channel 6 works great.
I noticed another thing relating to this problem: When WiFi is enabled but not used, the light blinks in a regular pattern. When the problem occurred, the WiFi light wasn't blinking. However, I was also sometimes able to connect when the light wasn't blinking. Now, the light never stops blinking. I guess the light is never supposed to stop blinking.