If you have EXAMINEFLD(*YES) specified on the RPGWIZ command, then the RPG Wizard not convert arthmetic operations if it cannot determine the field lengths/types used in the operations.
Please make sure your library list is set properly so the RPG Wizard can find any external field definitions (ie database fields, display file fields, copy books, etc.).
If your library list is set properly, then some arithmetic operations may still not be converted because of special considerations.
For instance, if an ADD or SUB operation does not convert, it is possible that the significant portion of the result field length is not large enough to hold the result. If you want to force the conversion of an ADD or SUB operation, even though the result field may overflow, then specify CVTADDSUB(*YES2) on the RPGWIZ command.