Partition switching/log purge problem

The senior sql people at my work are not here today and I need to figure out why this job keeps failing. It has to do with partition switching and I am not very familiar with that.

Here is the code from the stored procedure that fails:

--all tables created

Declare 
	@ArchiveCount as bigint
	, @MoveArchive as bigint
	, @totalCount as bigint
Declare 
	@AfterArchiveCount as bigint
	, @AfterMoveArchive as bigint
	, @AftertotalCount as bigint
Declare 
	@dt as int
	, @Purge as tinyint
	, @ct as bigint
	, @reprocess as int
Declare 
	@DaystoKeep as int

Set @DaystoKeep = 15

Set @reprocess = 0;

-- check to see if table is not empty
Set @MoveArchive = (select count(*) from Purge.OrderAllocatorLog)

if (@MoveArchive>0)
	begin
	Set @reprocess = 1;
	goto ProcessData
	end

FinishProcess:

Set @Purge = (Select datepart(day,getdate()))
Set @Purge = @Purge - 1

If (@Purge = 0)
	Set @Purge = 31;
	
Set @ct = (select count(*) from dbo.OrderAllocatorLog where Purge = @Purge)
	
While (@ct = 0)
	Begin
	Set @Purge = @Purge - 1
	Set @ct = (select count(*) from dbo.OrderAllocatorLog where Purge = @Purge)
	
	if (@Purge = 27)
		Begin
		Set @ct = -1
		Set @Purge = 99		
		End 
		
	If 	((@ct = 0) and (@Purge =0))
		Goto EndNow

	End

if ((@Purge > 0) and (@Purge < 32))
	Begin

	set @dt = (SELECT $PARTITION.OrderAllocatorLogPF1 (@Purge))

	--select @dt

	Truncate table Purge.OrderAllocatorLog

	ALTER TABLE dbo.OrderAllocatorLog SWITCH PARTITION @dt TO Purge.OrderAllocatorLog

ProcessData:

	Set @ArchiveCount = (select count(*) from dbo.OrderAllocatorLogArchive)

	Set @MoveArchive = (select count(*) from Purge.OrderAllocatorLog)

	Set @totalCount = @ArchiveCount + @MoveArchive

	if (@MoveArchive > 0)
			Begin
	
			INSERT INTO [CMOP].[dbo].[OrderAllocatorLogArchive]
				([ID],[DateAndTime],[MessageText])
			Select [ID],[DateAndTime],[MessageText]
				from Purge.OrderAllocatorLog
           
			Set @AfterArchiveCount = (select count(*) from dbo.OrderAllocatorLogArchive)
	
			If (@AfterArchiveCount <> @totalCount)             
				Begin
				INSERT INTO [CMOP].[dbo].[OrderAllocatorLogArchive]
					([ID],[DateAndTime],[MessageText])				
				Select oal.[ID],oal.[DateAndTime],oal.[MessageText]
					from Purge.OrderAllocatorLog oal 
						left join [dbo].[OrderAllocatorLogArchive] oala
						on oal.ID = oala.ID
						and oal.DateAndTime = oala.DateAndTime
					where oala.ID is null
				End 
			Else IF (@AfterArchiveCount = @totalCount)             
				Begin
				Truncate table Purge.OrderAllocatorLog
				End 
           
			End
	end

if (@reprocess = 1)	
	Begin
	set @reprocess = 0;
	goto FinishProcess
	End

EndNow:
	
Delete from	[dbo].[OrderAllocatorLogArchive]
where DateAndTime < getdate()- @DaystoKeep	

Select allOpen in new window

When this runs, it gives an error that the scalar variable @dt must be declared. But from what I can see it is being declared. The exact point that the job fails at is line 82, when it tries to ALTER TABLE and switch the partition.

Can someone help me understand what the problem is? We have this same job running on other servers and it works fine.

Thanks