@sharnaye1802 I've moved your post to the Sims 3 PC tech section.
This sometimes happens, for no apparent reason. The only way to fix it is to go through EA customer support: you can upload screenshots of your email confirmation and order history on ea.com to a live chat session. It's usually simple enough for a support rep to fix.
https://help.ea.com/en/contact-us/
Due to the current situation, support is on reduced hours, with phone calls unavailable entirely and live chat only open from 9 am to midnight GMT. Additionally, support has intermittently been down for the past week or two. I'm sorry I don't have a better suggestion other than trying again, but there's nothing anyone on this forum can do about a product key issue.
Just in case though, you can try clearing your browser cache and checking to see whether Roaring Heights is already on your store account. Please also try to add the product key again, copying and pasting the characters into the Redeem a Code window rather than retyping them. This is just to cover the first couple of suggestions support will probably give you when you do get in touch.
