MPLS must be configured on a VLAN before it can be used to transmit or receive MPLS-encapsulated frames. By default, MPLS is not configured on a newly created VLAN.
If you have enabled MPLS on an OSPF interface that is used to reach a particular destination, make sure that you enable MPLS on all additional OSPF interfaces that can reach that same destination (for example, enable MPLS on all VLANs that are connected to the backbone network).