Since orders are activated automatically without errors for most everyone, its usually a user error if your order has not activated, such as entering the wrong SteamID, or entering the StreamID in the wrong format.
SteamID's must be entered in the SteamID format, such as STEAM_0:0:12345678
DO NOT enter your SteamID in the SteamID64 Long format, such as 76561197978825530
DO NOT enter your Steam login username or Steam profile link as you SteamID.
For help with finding or converting your SteamID to the correct format, you can use this tool: https://steamid.io/
If you double-checked that your SteamID is correct on your Orders page and something is still not working, please Open a New Request here to get assistance: Billing Support Tickets.