Most important, you need to make sure you have the right version, as there are 2 standalone versions available (e-sellerate and fastspring), If your code starts OOTP20- then you have the e-sellerate version and need to be sure you have that version downloaded. If it does not, then you likely have the fastspring version which is a separate download. You can find links to both versions here:
https://forums.ootpdevelopments.com/...d.php?t=306707