What encryption is your router using? Technically WPA2 with TKIP is non-standard, and I've seen spurious reports of it not working on some devices. WPA and TKIP were compromised several years back, so the world moved from WPA with AES or TKIP, to WPA2 with AES. (Don't even bother with WEP - that can be brute-forced in less than an hour with modern computers).
Any modern router using a pre-shared key (PSK) should be set to WPA2 with AES, and any devices which don't support WPA2 with AES should be upgraded or replaced.