Check the encryption method on your wireless security. Nintendo likes TKIP and apparently hates AES. I had to switch the encryption before my Switch could connect - it's lousy because the PS4 seems to hate TKIP and has shoddy connection, so now I had to buy an ethernet cable to connect the PS4 and still have my Switch connect to my router.
The switch doesn't recognize tkip!
With aes the connection appears but not connect with the router!