Check if BGP peer is up:

show ip bgp vpnv4 vrf [vrf name] summary | i Neighbor|[neighbor IP]

Check if PIM neighborship is up:

show ip pim vrf [vrf name] neighbor [interface]

Check if they are joining anything:

show ip mroute vrf [vrf name] | i [interface]

show ip mroute vrf [vrf name] | i [interface] | i [multicast group IP]

show ip mroute [muticast group IP] »> to check for joins

*look for interface in Outgoing Interface List (aka OIL)

*check uptime

Check ACL and make sure they're permitted to join multicast group

show ip access-list [ACL name] | i [multicast group IP]

IOS XR

Check if BGP peer is up:

show bgp vrf [vrf name] summary | i [neighbor IP]

Check if PIM neighborship is up:

show pim vrf [vrf name] neighbor [interface]

Check if they are joining anything:

show mrib vrf [vrf name] ipv4 route

Check ACL and make sure they're permitted to join multicast group

show access-lists [ACL name]

Additional commands:

show mfib vrf [vrf name] interface [interface name] route | i Flags: $

show mfib vrf [vrf name] interface [interface name] route | i Flags: C