Anything in the default trace or sys.dm_exec_requests when this is happening?
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For fun, a variation of Chris's solution
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DECLARE @BINID VARBINARY(16) = NEWID();
;WITH BINARY_STUFF(DHASH,BINDATA,BINID)
AS
(
  SELECT CONVERT(CHAR(64),HASHBYTES('SHA2_512',CONVERT(VARCHAR(36),@BINID,0)),2),CONVERT(VARCHAR(36),@BINID,0),@BINID UNION ALL
  SELECT CONVERT(CHAR(64),HASHBYTES('SHA2_512',CONVERT(VARCHAR(36),@BINID,1)),2),CONVERT(VARCHAR(36),@BINID,1),@BINID UNION ALL

Simply remove the date from the group by clause
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SELECT
    PD.ID
,PD.country
,COUNT(*) AS Login_frequency
FROM        #promoter_details        PD
INNER JOIN    #login_info                LI
ON            PD.ID                =    LI.emp_id
GROUP BY...

Quick suggestion
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SELECT
    PD.ID
,PD.country
,COUNT(*) AS Login_frequency
,CONVERT(DATE,LI.login_server_time,0) AS Login_Date
FROM        #promoter_details        PD
INNER JOIN    #login_info                LI
ON            PD.ID                =    LI.emp_id
GROUP BY PD.ID
  ...

At home I use these from Harman Kardon, very good sound indeed
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