Here is a solid breakdown of the differences regarding the "New" status of these codes.
This is the hard path – proceed with caution. Here is a solid breakdown of the differences
Following the shutdown of original multiplayer servers (Quazal), all versions of CoH 1 were merged into a single client: Company of Heroes (New Steam Version) Content Unlocking : Activating an Opposing Fronts Spend $6 on a new Retail Code from a digital store
If you find your 2007 Product Key in a drawer, do not spend hours troubleshooting. Spend $6 on a new Retail Code from a digital store. Your time is worth more than the friction. (works for some late retail prints):
Because Opposing Fronts is an older game, some disreputable sellers list "New Retail Code" but actually send a photo of a used Product Key from a thrift store box.
(works for some late retail prints):