try this. You need a group by when you have a function.

Select Max(opseq) As opseq, 
wkctr, opstc 
From findMOInfoQuery2 
Where opstc = '20' InTo Cursor findMOInfoQuery3
group by wkctr, opstc

>This error is being generated
>
>SQL: GROUP BY clause is missing or invalid
>
>By this code
>
>Select Max(opseq) As opseq, wkctr, opstc From findMOInfoQuery2 Where opstc = '20' InTo Cursor findMOInfoQuery3
>
>Why would this happen?