NETGEAR M4100-D12G Port Authentication with tag and untag client

Hi

So I have this question about Port Authentication on this switch

If I try by a VLAN the client has to this switch nothing happens when 802.1X is enabled but if I try by untag it Authorizes me and works! And my client VLAN's work too!

So this switch being old I take it you can only be Authorized by untag? And then allows all VLAN's?

Thanks to anyone who knows