When selecting one from a parameter, it worked. When selecting multiple from a parameter, it creashed

Thank you in advance for your help.

I have an integer parameter called @Employees.

When I select one value from a parameter, it worked.  When I select multiple values from a parameter, the report failed.

I am using a function called fnParseString_udf to separate my parameter by ",".

My Query is in the stored procedure.

Example stored procedure:

CREATE PROCEDURE [cu].[spBICLDI]
 	@Employees INT

AS

SELECT 
	
'LoanNumberAccountNumber' = CONCAT(LoanNoteNumber,' - ', AccountNumber)
	
FROM TableA
	
WHERE @InsuranceType = CASE WHEN @InsuranceType IN ('CLDI') THEN CLDIIndicator
			    WHEN @InsuranceType IN ('GAPIWS') THEN GAPIWSIndicator
			END
	
AND LoanCreatedByUser IN (SELECT * FROM cu.fnBIparseString_udf(@Employees,','))

Sample of Employees parameter:

Name: Employees

Prompt: Employees

Data Type: Integer

Allow Multiple Values = Yes

Visible = Yes

=====================================

Available Values: Get Values from a query

Dataset: Employees

Value Field: TellerNumber

Label Field: Name

======================================

Default Values: Get Values from a query

Dataset: Employees

Value Field: TellerNumber

Sample of data in Employees Dataset: