Inputting DLsite Points Serial Code Displays An Error

Please confirm the following points:

• Are you on the correct page?
  Provided below is the correct page for converting serial codes into DLsite Points.
  [ DLsite: Serial Code input ]
  Please note that Bitcash, Webmoney, Gift Cards, etc. are processed via different pages.
• Have you input the code correctly?
  As serial codes are case-sensitive, please accurately copy and paste them into the input field.
  Take care that there are no spaces on the front / end, and that capitalization is unaltered.
• Have you tried waiting?
  There are cases where attempting to input the serial code immediately upon purchase may result in an error.
  Time will often resolve such issues, so we advise waiting and trying again.
• Have you tried a different browser / device?
  It is possible that the issue is specific to your system environment.
  If the above steps do not resolve the issue at hand, please try again with a different browser / device.