Stored Procedure works when executed manually but not via trigger - sql-server

Question

So I created a Stored Procedure in SQL that does 4 things
Create Order into Customer Order table
Create Order lines on Customer Order Line table
Update Auto number column by taking current value and adding 1
Update Purchase Order with Customer Order ID
Sends email to notify that an order has been created.
It works awesome if I execute each part separately or execute the whole Stored Procedure manually by sending command EXEC dbo.POIMPORT_UK #PO_NUM = 123456
But when I create a PO and it triggers the inserts, query 1,3,4,5 work but 2 doesn't for some reason. I can only get it to go if I fire off that procedure manually. Any thoughts?
USE [RIPTST]
GO
/****** Object: StoredProcedure [dbo].[POIMPORT_UK] Script Date: 8/20/2018 11:21:23 AM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER proc [dbo].[POIMPORT_UK]
#PO_NUM NVARCHAR(15)
AS
SET NOCOUNT ON
--For synchronization machine id placement
--Query 1
INSERT INTO CUSTOMER_ORDER(ID, CUSTOMER_ID, SITE_ID, SELL_RATE, BUY_RATE,
TERMS_NET_TYPE, TERMS_DISC_TYPE, FREIGHT_TERMS, BACK_ORDER, STATUS,
POSTING_CANDIDATE, MARKED_FOR_PURGE, CURRENCY_ID, CUSTOMER_PO_REF,
WAREHOUSE_ID, DESIRED_SHIP_DATE) SELECT (SELECT Next_number FROM
NEXT_NUMBER_GEN where rowid =
'72'),'ABECO','101RIPUS','1.0','1.0','A','A','P','N','F','N','N','(USD)
$',ID,'CROM',Getdate() FROM PURCHASE_ORDER WHERE ID = #PO_NUM
--Query 2
INSERT INTO CUST_ORDER_LINE
(CUST_ORDER_ID,LINE_NO,PART_ID,LINE_STATUS,ORDER_QTY,USER_ORDER_QTY,
SELLING_UM,UNIT_PRICE,SITE_ID,MISC_REFERENCE,PRODUCT_CODE,COMMODITY_CODE,
DRAWING_ID,DRAWING_REV_NO,MAT_GL_ACCT_ID,LAB_GL_ACCT_ID,BUR_GL_ACCT_ID,
SER_GL_ACCT_ID,GL_REVENUE_ACCT_ID,TOTAL_AMT_ORDERED,ENTERED_BY,WAREHOUSE_ID)
SELECT(select id from customer_order where CUSTOMER_PO_REF = #PO_NUM),
LINE_NO,PURC_ORDER_LINE.PART_ID,'A',ORDER_QTY,USER_ORDER_QTY,
PURCHASE_UM,PURC_ORDER_LINE.UNIT_PRICE,'101RIPUS',PART.DESCRIPTION,
PART.PRODUCT_CODE,PART.COMMODITY_CODE,PART.DRAWING_ID,PART.DRAWING_REV_NO,
PART_SITE.MAT_GL_ACCT_ID,PART_SITE.LAB_GL_ACCT_ID,PART_SITE.BUR_GL_ACCT_ID,
PART_SITE.SER_GL_ACCT_ID,
(SELECT REV_GL_ACCT_ID FROM PRODUCT WHERE CODE = PART.PRODUCT_CODE),
USER_ORDER_QTY*PURC_ORDER_LINE.UNIT_PRICE,'SYSADM',
PART_SITE.PRIMARY_WHS_ID From PURC_ORDER_LINE
Inner Join PART On PART.ID = PURC_ORDER_LINE.PART_ID
Inner Join PART_SITE On PART_SITE.PART_ID = PART.ID
WHERE PURC_ORDER_ID = #PO_NUM AND PART_SITE.sITE_ID = '101RIPUS'
--Query 3
Update NEXT_NUMBER_GEN Set Next_number = Next_number + 1 where rowid = '72'
--Query 4
Update PURCHASE_ORDER Set SALES_ORDER_ID = (select id from customer_order where CUSTOMER_PO_REF = #PO_NUM) where id = #PO_NUM
--Query 5
Declare #PO NVARCHAR(15) = #PO_NUM
Declare #CO NVARCHAR(15) = (select id from customer_order where CUSTOMER_PO_REF = #PO)
Declare #MYBODY VARCHAR(MAX) = 'Hello Test CSR,
A new internal order has been created for Ripley UK.
Test US Customer Order Number: ' + #CO +
'
Test UK Purchase Order Number: ' + #PO
EXEC msdb.dbo.sp_send_dbmail #profile_name='office365',
#recipients='test#test.com',
#subject='Test UK - Internal Order',
#body= #MYBODY
SET NOCOUNT OFF
Insert Trigger
USE [RIPTST]
GO
/****** Object: Trigger [dbo].[INSERT_PURCHASE_ORDER] Script Date: 8/20/2018 1:42:15 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
ALTER trigger [dbo].[INSERT_PURCHASE_ORDER] ON [dbo].[PURCHASE_ORDER] FOR INSERT AS
DECLARE
#nRcd INT,
#ID NVARCHAR(15),
#VENDOR_ID NVARCHAR(15),
#SITE_ID NVARCHAR(15),
#STATUS NCHAR,
#TOTAL_AMT_ORDERED DEC(15,2),
#TOTAL_AMT_RECVD DEC(15,2),
#SELL_RATE DEC(17,8),
#nCurrDigits INT,
#sEntityID NVARCHAR(15),
#ORDER_DATE DATETIME
SELECT #nRcd = 0
SET NOCOUNT ON
DECLARE PURCHASE_ORDER_INS CURSOR LOCAL FOR SELECT ID, VENDOR_ID, STATUS, TOTAL_AMT_ORDERED, TOTAL_AMT_RECVD, SELL_RATE, ORDER_DATE, SITE_ID FROM INSERTED
OPEN PURCHASE_ORDER_INS
FETCH PURCHASE_ORDER_INS INTO #ID, #VENDOR_ID, #STATUS, #TOTAL_AMT_ORDERED, #TOTAL_AMT_RECVD, #SELL_RATE, #ORDER_DATE, #SITE_ID
WHILE (#nRcd = 0 and ##FETCH_STATUS <> -1)
BEGIN
EXEC EXE_DETECT_EVENT 'P', #ID, NULL, NULL, 'I'
If #TOTAL_AMT_ORDERED + #TOTAL_AMT_RECVD != 0
SELECT #nRcd = 30881
If #nRcd = 0 And (#STATUS = 'R' Or #STATUS = 'F') And #TOTAL_AMT_ORDERED > #TOTAL_AMT_RECVD
BEGIN
select #nCurrDigits = c.i_curr_digits, #sEntityID = s.entity_id from CURRENCY c, ACCOUNTING_ENTITY ae, SITE s where s.id = #SITE_ID and ae.id = s.entity_id and ae.functional_currency_id = c.id
IF NOT EXISTS ( SELECT VENDOR_ID FROM VENDOR_ENTITY WHERE vendor_id = #VENDOR_ID and entity_id = #sEntityID )
INSERT INTO VENDOR_ENTITY ( VENDOR_ID, ENTITY_ID ) VALUES ( #VENDOR_ID, #sEntityID )
update VENDOR_ENTITY set
total_open_orders = total_open_orders + ROUND((#TOTAL_AMT_ORDERED - #TOTAL_AMT_RECVD) * #SELL_RATE, #nCurrDigits),
open_order_count = open_order_count + 1
where vendor_id = #VENDOR_ID and entity_id = #sEntityID
END
UPDATE VENDOR set last_order_date = #ORDER_DATE where id = #VENDOR_ID
FETCH PURCHASE_ORDER_INS INTO #ID, #VENDOR_ID, #STATUS, #TOTAL_AMT_ORDERED, #TOTAL_AMT_RECVD, #SELL_RATE, #ORDER_DATE, #SITE_ID
END
BEGIN
IF #VENDOR_ID = 'RIP01' AND #SITE_ID = '111RIPUK'
EXEC dbo.POIMPORT_UK #PO_NUM = #ID
END
DEALLOCATE PURCHASE_ORDER_INS
IF (#nRcd <> 0) RAISERROR('VMFG-%d error in trigger INSERT_PURCHASE_ORDER', 16, -1, #nRcd)
IF (#nRcd <> 0 Or ##ERROR <> 0) ROLLBACK TRANSACTION