I copied and pasted the item number as I usually do, but the number is showing as invalid. It is for this item:
1994 Pro Tags #124 Ronnie Lott PSA 10 GEM MINT Jets, 49ers

Hello Adam,
Thank you for your question about the "Invalid Item Number" message. We jumped on this issue as soon as you wrote and resolved it. Please let us know if you see it again.
Also - instead of cutting and pasting the item number, you can use our "Slam-It" toolbar, located at the bottom left of your Dashboard.
Please let us know if you have any other questions, or require other assistance. We are happy to help.