For native vlan to work

[Iloveyou]

Sometimes I need to put untagged in the AP to work.

Sometimes I need to put vlan 1 in the AP to work.

Why?

I am referring to management vlan?

[Mark Elsen]

 - Untagged and vlan 1 are unrelated , the first referring to  a (the) native vlan , on an access port (usually)

 M.

[Joseph W. Doherty]

By default, VLAN 1 is the native and untagged VLAN on a trunk.

On an access port, the data VLAN is also untagged.

So, for an untagged AP to work, it would need to work with a port and exchanged untagged frames, VLAN, itself, shouldn't matter beyond does the VLAN allow the AP access to resources it needs.