Try and do a manual poll, rediscover, or list resources of nodes located on the remote poller.
some versions (10.4, 10.5 I think) make use of MSMQ to do the communications between the App server and the poller.
MSMQ broke = you get an error about not being able to force a poll.
note, regular polling and rediscovery work fine, you just can't do any of the on-demand tasks.