Replication Monitor Missing Subscriptions in Watch List

In Replication Monitor, for one of our publications (transactional replication), none of the subscriptions are showing up in the Subscription Watch List. This is new behavior that just started recently. The other publications associated with this distributor don't exhibit this behavior, the subscriptions are visible under the Subscription Watch List tab. I can reproduce similar behavior using the Sp_replmonitorhelpsubscription SP. When executing this using the @publisher that is not returning results in the Replication Monitor, no results are returned. But when using the @publisher that do show subscriptions, results are returned. I've confirmed in the subscription database for this affected publisher that transactional replication is functioning as expected, commands are being delivered, row counts are in sync. Is there anything that can be done to get the subscriptions to appear again for the affected publisher? The only thing I can think of doing is deleting the subscription and publication and starting over, since some metadata must be missing, but that requires a downtime and seems unnecessary. Version: Microsoft SQL Server 2008 R2 (SP2) - 10.50.4000.0