Ok, next step is to join your data table to this hourly breakdown table. Try first with a full outer join as shown, this helps pinpoint any issues with aligning your data table with the buckets:
;WITH Headers AS (
 SELECT *
 FROM MST_SESSION_TEST p
 CROSS APPLY (
  SELECT TOP(1+DATEDIFF(HOUR,SES_START,SES_END))
   HourStart = DATEADD(HOUR,n,m.SessionStart),
   HourEnd = DATEADD(HOUR,n+1,m.SessionStart)
  FROM (VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12)) d (n)
  CROSS APPLY (SELECT SessionStart = DATEADD(MINUTE,DATEDIFF(MINUTE,'20000101',SES_START),'20000101')) m
 ) x
)
SELECT h.*, c.REC_ID, c.SES_NOTE, c.REC_DATETIME, c.REC_PRODUCT, c.REC_TOTAL
FROM Headers h
FULL OUTER JOIN MST_REC_TEST c
 ON c.SES_NOTE = h.SES_NOTE
 AND c.REC_DATETIME >= HourStart 
 AND c.REC_DATETIME < HourEnd