unclear status of access points

Hi all,

I have 3 AP6 420 managed by Central. FW is 1.4.1819 (actual).

1. Question: The Dashboard says, that 1 AP is unconfigured. What does it mean and how to change that?

2. Question: in Access Point List: 1 AP is "up to date", 2 APs are waiting to update since days. How to force an update? Reboot doesn't solve.

3. Question: I want to mesh the APs, because 1 AP is unable to get connected via cable. Therefore I created a mesh network with 2 APs. I want to add the 3rd AP. But after config the system says "Your mesh network has now configured. Click save". but save button is greyed out... So I cannto save. No error message is available...

any hints?

Thanks

Gernot