Value Set not returning any value to Fast Formula

Summary:

I have many value sets that work just fine in other fast formulas, but for some reason this one is not returning any data - even if I hardcode the WHERE clause

Content (required):

l_ctfn_rcvd = GET_VALUE_SET('IUH_GET_ENRT_CTFN_PRVDD','|=PERSON='''||l_person_id||''''||'|CTFN_CD='''||c_ctfn_cd||''''||'|PLAN_NM='''||t_plan_name||'''') 

I have confirmed via log messages that all the parameters have values when the FF runs, but even if I remove all the parameters and replace them with hardcoded values still I get nothing returned.