proc Sql Case Statement returning Null values

Question

Can someone look at my Proc Sql and tell me why the below case staement is returing Null values in the data? I have never seen this, there are no errors, the code runs and the case statement value (Enrollment_Period) in the data is Null. Any ideas or solutions ?

proc sql;
        create table Data_Active as
           select distinct
                e.cova_evnt_efcv_dt as cova_evnt_efcv_dt Format=MMDDYYS10.,
                e.cova_evnt_eprn_dt as cova_evnt_eprn_dt Format=MMDDYYS10.,
                year(cova_evnt_efcv_dt) as Year,
                month(cova_evnt_efcv_dt) as Month,
                Case
                when 'Month' = "1" then "AEP"
                when 'Month' = "2" then "OEP"
                when 'Month' = "3" then "OEP"
                when 'Month' = "4" then "LockIn"
                when 'Month' = "5" then "LockIn"
                when 'Month' = "6" then "LockIn"
                when 'Month' = "7" then "LockIn"
                when 'Month' = "8" then "LockIn"
                when 'Month' = "9" then "LockIn"
                when 'Month' = "10" then "LockIn"
                when 'Month' = "11" then "LockIn"
                when 'Month' = "12" then "LockIn"
                end as Enrollment_Period,