I had a similar problem with one pesky device. Kept telling me to check the password. Phones worked, laptop worked etc..
Check security settings.... first i turned security to "none" on the wifi. That fixed it. Then I tried different combinations until I had the wifi set on WPA2 personal and the device on auto wpa2.... (yours may be different) and Linksys support wanted to charge me $30 to help!
Another thing could be the device is 2.4 Ghz and the wifi is 5Ghz or 2.4 not set up on wifi... or vice versa.