ERROR: key not found in SQL when trying to pass the result of a CTE as a function parameter

[JS_L]

Hi Community,
I try to pass the result of a CTE as a function parameter as code below

WITH t1 AS (
    SELECT array_join(collect_list(output), ',') AS x
    FROM my_catalog.my_db.get_x(:startTime, :endTime)
)
SELECT 'AM_offline' as Type, CASE WHEN offline_ratio > 1.5 THEN 'no-Go' ELSE 'Go' END as Status
FROM my_catalog.my_db.get_ratio (
    _startTime => :startTime, 
    _endTime => :endTime, 
    _x => (SELECT x FROM t1 LIMIT 1)
)

However, I encounter the key not found error. Can someone tell me, what is the reason of such error?

key not found: 863

Thank you.