Hello,
I would say first check the live logs to compare the details like authorization results between generic user account vs sponsor portal account to confirm they are truly getting the same auth results because it may be possible sponsor accounts are getting a different results which contains a session timeout value attribute for the controller vs generic accounts hitting the default value on the controller.
You can also check the particular sponsor groups the users belong under Work centers > Guest access > portals & components . This gives you an option to define attributes so may be getting defined there
On the wireless controller, you can also enable and set a session timeout value which will apply to all users. The max value for this is 24 hours.
- If you have an AireOS platform , this will be in the advanced tab of the WLAN
- If you have a 9800, this will be in the policy profile advanced tab