Another possibility is a mismatch between the collection ID in the catalog and the collection ID in the collection table. OAM checks for this condition when the OAM address space is started. Check your system log during OAM address space initialization for message CBR9030I or other messages that might indicate a problem with the catalog.
LISTCAT ENTRIES('collection_name') ALLVerify that the DIRECTORYTOKEN matches the storage group name for qualifier GROUPxx on the ISMF storage group definition panel.
Indicate "ACTIVE" as the SCDS name when listing Object storage group information. The storage group name in the catalog entry must also match the storage group name (ODCLSGNM) in the collection table entry for the collection associated with the object.