In customer environment, Ae bundle was down but its all member interfaces were up.

AE bundle is down and all member links are up.

LAB-RE0> show interfaces terse | grep ae26 

 xe-5/1/20.0       up  up  aenet  --> ae26.0

 xe-5/1/21.0       up  up  aenet  --> ae26.0

 xe-5/1/22.0       up  up  aenet  --> ae26.0

 xe-5/1/23.0       up  up  aenet  --> ae26.0

 ae26          up  down

 ae26.0         up  down inet   184.183.211.28/31

LAB-RE0> show lacp interfaces ae26 

Aggregated interface: ae26

LACP state:    Role  Exp  Def Dist Col Syn Aggr Timeout Activity

xe-5/1/20   Actor  No  Yes  No  No  No  Yes   Fast  Active

xe-5/1/20  Partner  No  Yes  No  No  No  Yes   Fast  Passive

xe-5/1/21   Actor  No  Yes  No  No  No  Yes   Fast  Active

xe-5/1/21  Partner  No  Yes  No  No  No  Yes   Fast  Passive

xe-5/1/22   Actor  No  Yes  No  No  No  Yes   Fast  Active

xe-5/1/22  Partner  No  Yes  No  No  No  Yes   Fast  Passive

xe-5/1/23   Actor  No  Yes  No  No  No  Yes   Fast  Active

xe-5/1/23  Partner  No  Yes  No  No  No  Yes   Fast  Passive

LACP protocol:    Receive State Transmit State     Mux State 

xe-5/1/20        Defaulted  Fast periodic      Detached

xe-5/1/21        Defaulted  Fast periodic      Detached

xe-5/1/22        Defaulted  Fast periodic      Detached

xe-5/1/23        Defaulted  Fast periodic      Detached

Verify LACP statistics.

Observed that there are no "Rx" packets increments for any of the member link:

LAB-RE0> show lacp statistics interfaces ae26 

Aggregated interface: ae26

  LACP Statistics:    LACP Rx   LACP Tx  Unknown Rx  Illegal Rx 

   xe-5/1/20         0    5391      0      0

   xe-5/1/21         0    5391      0      0

   xe-5/1/22         0    5391      0      0

   xe-5/1/23         0    5391      0      0

When LACP RX is 0, we should verify configuration/ ae bundle status on other side.

Since physical interfaces are up, we do not suspect L1 issue.