SQL - Syntax Queries

Hi EE,

I have the following query:

SELECT
    A.[VENDOR NAME] AS 'VENDOR NAME',
    A.[VENDOR NUMBER] AS 'VENDOR NUMBER'
FROM
    (SELECT
        PURCHTABLE.PURCHNAME AS 'VENDOR NAME',
        PURCHTABLE.ORDERACCOUNT AS 'VENDOR NUMBER',
        COUNT(DISTINCT PURCHTABLE.PURCHID) AS 'PURCHASE ORDER',
        COUNT(PURCHLINE.LINENUMBER) AS 'NUMBER OF LINES',
        SUM(PURCHLINE.LINEAMOUNT) AS 'PO PRICE TOTAL',
        DATEDIFF(dd, PURCHTABLE.CONFIRMEDDLV, MAX(VENDPACKINGSLIPJOUR.DELIVERYDATE))-(DATEDIFF(wk, PURCHTABLE.CONFIRMEDDLV, MAX(VENDPACKINGSLIPJOUR.DELIVERYDATE)) * 2)-(CASE WHEN DATENAME(dw, PURCHTABLE.CONFIRMEDDLV) = 'Sunday' THEN 1 ELSE 0 END)-(CASE WHEN DATENAME(dw, MAX(VENDPACKINGSLIPJOUR.DELIVERYDATE)) = 'Saturday' THEN 1 ELSE 0 END) AS 'DAYS LATE'
    FROM
    PURCHTABLE
    JOIN
    PURCHLINE ON PURCHLINE.PURCHID = PURCHTABLE.PURCHID
    JOIN
    VENDPACKINGSLIPJOUR ON VENDPACKINGSLIPJOUR.PURCHID = PURCHTABLE.PURCHID
    WHERE
    PURCHTABLE.DELIVERYDATE >= '2019-01-01'
    AND
    PURCHTABLE.DELIVERYDATE <= '2019-01-20'
    AND
    PURCHTABLE.ORDERACCOUNT = 'FDS5834') as A
   
GROUP BY  
A.[VENDOR NAME],
A.[VENDOR NUMBER],
A.[PURCHASE ORDER],
PURCHTABLE.CONFIRMEDDLV

Getting the following errors

Msg 8120, Level 16, State 1, Line 6
Column 'PURCHTABLE.PURCHNAME' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.
Msg 4104, Level 16, State 1, Line 29
The multi-part identifier "PURCHTABLE.CONFIRMEDDLV" could not be bound.

Both these tables/columns exist and the PURCHTABLE.PURCHNAME' have appropriate aliases.

Any assistance is welcome.

Thank you.