Best guess

SELECT up.User_Id, up.User_FullName, up.Email, up.User_Group ,i.Event_ID

FROM User_Profile a

JOIN User_Profile up ON up.User_Group = a.User_Group

JOIN Group_Lookup g ON g.LOB_GRP = up.User_Group

JOIN Impacted_LOB i ON i.LOB_CD = g.LOB_CD

Really need test data and expect results to form a better solution.