SQL Server stored procedure to JSON error - sql-server

Question

I am trying to write the following stored procedure:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[spInsertAudit]
(#val1 VARCHAR(100),
#val2 VARCHAR(200))
AS
BEGIN TRY
DECLARE #return_value varchar(max)
/************************************/
/* The Query */
/************************************/
EXEC [dbo].[SerializeJSON]
'INSERT INTO tLogin (EMP, LoginInTime)
VALUES (#val1, #val2)'
END TRY
BEGIN CATCH
/************************************/
/* Get Error results back */
/************************************/
EXEC [dbo].[SerializeJSON]
'SELECT ERROR_NUMBER() AS ErrorNumber,
ERROR_SEVERITY() AS ErrorSeverity,
ERROR_STATE() AS ErrorState,
ERROR_PROCEDURE() AS ErrorProcedure,
ERROR_LINE() AS ErrorLine,
ERROR_MESSAGE() AS ErrorMessage'
END CATCH
The SerializeJSON stored procedure (found here) is this:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[SerializeJSON]
(#ParameterSQL AS VARCHAR(MAX))
AS
BEGIN
DECLARE #SQL NVARCHAR(MAX)
DECLARE #XMLString VARCHAR(MAX)
DECLARE #XML XML
DECLARE #Paramlist NVARCHAR(1000)
SET #Paramlist = N'#XML XML OUTPUT'
SET #SQL = 'WITH PrepareTable (XMLString)'
SET #SQL = #SQL + 'AS('
SET #SQL = #SQL + #ParameterSQL + 'FOR XML RAW,TYPE,ELEMENTS'
SET #SQL = #SQL + ')'
SET #SQL = #SQL + 'SELECT #XML=[XMLString]FROM[PrepareTable]'
EXEC sp_executesql #SQL
, #Paramlist
, #XML = #XML OUTPUT
SET #XMLString = CAST(#XML AS VARCHAR(MAX))
DECLARE #JSON VARCHAR(MAX)
DECLARE #Row VARCHAR(MAX)
DECLARE #RowStart INT
DECLARE #RowEnd INT
DECLARE #FieldStart INT
DECLARE #FieldEnd INT
DECLARE #KEY VARCHAR(MAX)
DECLARE #Value VARCHAR(MAX)
DECLARE #StartRoot VARCHAR(100);
SET #StartRoot = '<row>'
DECLARE #EndRoot VARCHAR(100);
SET #EndRoot = '</row>'
DECLARE #StartField VARCHAR(100);
SET #StartField = '<'
DECLARE #EndField VARCHAR(100);
SET #EndField = '>'
SET #RowStart = CharIndex(#StartRoot, #XMLString, 0)
SET #JSON = ''
WHILE #RowStart > 0
BEGIN
SET #RowStart = #RowStart + Len(#StartRoot)
SET #RowEnd = CharIndex(#EndRoot, #XMLString, #RowStart)
SET #Row = SubString(#XMLString, #RowStart, #RowEnd - #RowStart)
SET #JSON = #JSON + '{'
-- for each row
SET #FieldStart = CharIndex(#StartField, #Row, 0)
WHILE #FieldStart > 0
BEGIN
-- parse node key
SET #FieldStart = #FieldStart + Len(#StartField)
SET #FieldEnd = CharIndex(#EndField, #Row, #FieldStart)
SET #KEY = SubString(#Row, #FieldStart, #FieldEnd - #FieldStart)
SET #JSON = #JSON + '"' + #KEY + '":'
-- parse node value
SET #FieldStart = #FieldEnd + 1
SET #FieldEnd = CharIndex('</', #Row, #FieldStart)
SET #Value = SubString(#Row, #FieldStart, #FieldEnd - #FieldStart)
SET #JSON = #JSON + '"' + #Value + '",'
SET #FieldStart = #FieldStart + Len(#StartField)
SET #FieldEnd = CharIndex(#EndField, #Row, #FieldStart)
SET #FieldStart = CharIndex(#StartField, #Row, #FieldEnd)
END
IF LEN(#JSON) > 0
SET #JSON = SubString(#JSON, 0, LEN(#JSON))
SET #JSON = #JSON + '},'
--/ for each row
SET #RowStart = CharIndex(#StartRoot, #XMLString, #RowEnd)
END
IF LEN(#JSON) > 0
SET #JSON = SubString(#JSON, 0, LEN(#JSON))
SET #JSON = '[' + #JSON + ']'
SELECT #JSON
END
When I execute the spInsertAudit stored procedure, I get this error:
Msg 102, Level 15, State 1, Line 8
Incorrect syntax near 'XML'.
So it did write to that table but for some reason it's not returning the JSON and having that error above....