Enchantment Does't Offer All Options

When you re-roll primary properties on a weapon, some of them are incredibly heavily weighted in the table of possible results. The elemental damage affixes are really tough to avoid getting because if you roll this off, a one-handed weapon that has 2000+ damage will go down to 450 damage. This is why the game tries to ensure you don’t get a result like that, by ensuring that you’ll pretty much always be offered at least one elemental damage affix whilst re-forging.

As TimberWolf alluded to, if you succeeded in doing so, your very next post would be asking why you can no longer kill stuff, and we’d be directing you to…

In short, the game’s trying to prevent you from doing this…

This is not a bug.
This is not a technical issue.
This is the game working exactly as intended.