All subscriptions are no longer appearing without any changes made in the environment. All of them continue to run. Trying to show a subscription created for an object this is what the view you get:

Changes in the metadata could lead to this behavior with the subscriptions not being shown.
Run the following SQL statement against the metadata with the subscriptions:
SELECT * FROM DSSCSSUBINSTwhere DSSCSSUBINST.PARENT_ID = '00000000000000000000000000000000'ANDDSSCSSUBINST.STATUS=0ORDER BY DSSCSSUBINST.CREATION_TIME ASC
UPDATE DSSCSSUBINST SET STATUS=1 WHERE STATUS=0 and DSSCSSUBINST.PARENT_ID = '00000000000000000000000000000000';