Im struggling to build a simple SuiteQL query with a join on product sizes. This works fine:

SELECT * FROM CUSTOMLIST_PSGSS_PRODUCT_SIZE

This returns an object that I expect:

{
  "links": [],
  "id": "249",
  "isinactive": "F",
  "name": "10.5B",
  "recordid": "249",
  "scriptid": "VAL_52294_4631649_842"
}

According to my record browser, this should be a join option on

Item

See Screenshot. Trying to pull it together in a simple query:

SELECT 
     Item.upcCode as barcode_value,
     Item.displayname as name,
     CUSTOMLIST_PSGSS_PRODUCT_SIZE.name as size
FROM Item
LEFT JOIN CUSTOMLIST_PSGSS_PRODUCT_SIZE on CUSTOMLIST_PSGSS_PRODUCT_SIZE.id=Item.custitem_psgss_product_size
WHERE 
     Item.upcCode IS NOT NULL
     AND Item.matrixtype = 'CHILD'
     AND Item.isInactive = 'F'

When I run this query, I get back

{
  "type": "<https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.4.1>",
  "title": "Bad Request",
  "status": 400,
  "o:errorDetails": [
    {
      "detail": "Invalid search query. Detailed unprocessed description follows. Search error occurred: Invalid or unsupported search.",
      "o:errorQueryParam": "q",
      "o:errorCode": "INVALID_PARAMETER"
    }
  ]
}

I can't for the life of me figure out what I'm doing wrong. I'm sure its something dumb. Does anyone spot anything here? Thanks in advance!