Environment : Instant AP deployment which uses PPPoE as Uplink.
PPPoE has been configured correctly but isn't used by Instant Access Point.
Below are possible causes for PPPoE uplink not being used :
Instant AP doesn't support PPPoE configuration changes on the fly - PPPoE configuration is picked up and used on boot up. If configuration is made; a reload is needed for new PPPoE related configuration to take effect.
DHCP has higher preference - PPPoE happens in parallel to DHCP. Therefore; IAP would support either DHCP or PPPoE uplink but not both. DHCP would be given higher priority over PPPoE. Thus in spite of a PPPoE valid configuration, IAP wouldn't use it if it gets an IP address via DHCP.
The resolution for above scenarios are :
Instant AP doesn't support PPPoE configuration changes on the fly - Reload Aruba Instant Access Point after making PPPoE config change.
DHCP has higher preference - Ensure DHCP is blocked on AP port so it wouldn't obtain IP via DHCP
If issue persist; please collect below command output and contact support ::
show ip interface brief
show pppoe config
show pppoe status
show uplink status
show log system
show log pppd