UDF not found when importing to Excel via Microsoft Query

I have created a UDF to return a scalar function within an SQL Select statement. The UDF references a procedure within a service program. The Select works fine when using SQL on the IBM i - Run SQL Scripts from Navigator, Run SQL Scripts from ACS (is that the same?), and green-screen STRSQL. But when I try to reference it from within Excel, using "Get external data" / "From other sources" / "From Microsoft Query", I get "SQL0204 - XX0504V in OELIB type *SRVPGM not found" (where XX0504V is in fact the name of the service program).

I have learned that the SQL0204 "not found" message can really mean something like parameter mismatch, so I have checked and tinkered with those to no avail. The connection defined in Excel has the same user ID and the same library list, plus the UDF name is qualified; I see no reason that it can't really be found. I suspect either a difference in syntax between the two SQL's (MS and IBM i) or something else relating to the connection definition. All other SQL which I have copied over in this way works fine; it seems to be only the UDF.

(I'm new on this list so forgive me if this has been addressed before; I was not able to find anything in the history.)

Thanks for any direction.

Bill Reed