purchasd invalid code

i purchased to picture books on the same day. the 1st code was accepted to no problem but the second code they said it was invalid i was deducted poimts for it , so its in my history as being fulfilled vut i tryr=ed the code again ab=n same thinh cog=de is invalid. so im n=ot happy because i wanted 2 bood=ks , i was deducted points and it says its been fullfillr=ed and it has ni=ot been , can someone clear thid up????