Running query against SQL Server with FreeTDS's bsqldb returns blank output
I suspect the one of the values is NULL, so the whole expression concatenation is NULL.

You'd need this:

CAST(ISNULL(PageGuid, '') as varchar(max)) + ',' + 
CAST(ISNULL(TenantGuid, '') as varchar(max)) + '/' +
CAST(ISNULL(OriginalFileGuid, '') as varchar(max))