Invalid length parameter passed to the LEFT or SUBSTRING function in Sql Server

While trying to execute the below query

Declare @t table (id int, string varchar(1000))

INSERT INTO @t (id, string)
SELECT 1, 'zxzzxx,ppppbppp,trtrtr,tyyt,hgghh,fefew,rewr,rwerer' 

;WITH test (id, lft, rght, idx)
AS 
(
        SELECT t.id
                ,LEFT(t.string, CHARINDEX(', ', t.string) - 1)
                ,SUBSTRING(t.string, CHARINDEX(', ', t.string) + 2, DATALENGTH(t.string))
                ,0
        FROM @t t
        UNION ALL
        SELECT c.id
                ,CASE WHEN CHARINDEX(', ', c.rght) = 0 THEN c.rght ELSE LEFT(c.rght, CHARINDEX(', ', c.rght) - 1) END
                ,CASE WHEN CHARINDEX(', ', c.rght) > 0 THEN SUBSTRING(c.rght, CHARINDEX(', ', c.rght) + 2, DATALENGTH(c.rght)) 
                        ELSE '' END
                ,idx + 1
        FROM test c 
        WHERE DATALENGTH(c.rght) > 0
)

select id, lft from test 

I am getting the below error

Msg 537, Level 16, State 2, Line 8
Invalid length parameter passed to the LEFT or SUBSTRING function.

but the same works for SELECT 1, 'the, quick, brown, fox, jumped, over, the, lazy, dog'

Please help

It seems to be a space missing between your words.

You are currently looking for charindex of ', ' not ','.

And the string does not have any match of ', '.