ISIS over L2VPN Frame-Relay P2P

Guys,

any idea why ISIS adj is not forming over L2VPN frame-relay P2P, but CLNS adj is forming?? Its seems like each CE isn't receiving LAN IIH packets from other end.

Network:

* R3 - (R1 - R2) - R4, with R3 and R4 as CE1 and CE2

R1#show xconnect all

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  HS=Hot Standby     RV=Recovering      NH=No Hardware

XC ST  Segment 1                         S1 Segment 2                         S2

------+---------------------------------+--+---------------------------------+--

UP     ac   Se2/0:341(FR DLCI)           UP mpls 2.0.0.1:341                  UP

UP     ac   Se2/0:342(FR DLCI)           UP mpls 2.0.0.1:342                  UP

R1#