It seems silly but I'm stumped after tearing up all the configuration options and researching. I can't find any way to prevent users having to log in via Sonicwall web authentication in addition to authenticating to wifi as well. Hoping someone else has seen this. Thanks!
Does the firewall rule allowing access to the Internet from your Wireless zone have a user requirement? It should be set to
On a somewhat related note, are you attempting to use a Single Sign On agent? You could alternately be having a problem with SSO requests getting blocked.