MyBB Community Forums

I have converted my forum from vbb 3.8.4 to mybb 1.4.11, I used Merge System Version 1.4 Beta 5.
Everything is good, but today I recognize that It has a problem when I set permission for each group in each forum or category.
I want Guest group can't view a category and in acp, I uncheck all check button (Can View?, Can Post Thread...) with Guest group and save.
But when I logout and test, I can see that category.
What's happening? Can you help me?

Can you printscreen the permissions setup?? Make sure the 'Use group default' option isn't checked.

Yes, I'm sure that Guest group which I unchecked is default group.
You can see my printscreen:

I set permission for category "Văn phòng đoàn" as the following picture:


But when I logout and test, category "Văn phòng đoàn" is still available for Guest group:


This is the first time I meet this error.

OK, can you click Edit Permissions next to the guest group on that page and make sure the 'Use custom permissions below' setting is checked. If it is, go to ACP > Configuration > Forum Home Options > Hide Private Forums? > make sure this is set to Yes. If that doesn't work, try setting the same permissions for the forums inside the forum you're currently editing.

Ok, I have done successfully, thank you very much.