Unavailable to select session maintenance manager after select "Cookie Insert"

Please try following steps:
(Case:Change "Persistence" 「COOKIEINSERT」to「SOURCEIP」）
1.Change Persistence to「COOKIEINSERT」at Virtual Server Persistence
Put into unique name as Cookie Name, then click "OK"
2.Delete "Cookie Name" at Virtual Server Persistence, then click "OK".
3.Change Persistence to「SOURCEIP」at Virtual Server Persistence, then click "OK". *1

*1When you change except for「SOURCEIP」,select「another persistence」then click "OK".