Hey Valaetoshiru, quite a few people are having issues with this, but i think i can help you fix this problem.
First of all, the obvious but sometimes missed, do check that you have logged in to the website on the top right. (i did at first for instance, i was too used to having my account saved so i don't have to reconnect)
if you see this on the top right after scrolling all the way up, there's the problem, if not, you'll see this :
If you're logged in, that's a good start, now to check the next step. Go to the "Campaigns & Perks" category, then scroll down and you should see something like this :
If you don't have any packages that appear for you, that means you may not have linked your account to your M3 purchase yet. In this case you'll have to go to the "My account" category and check this
click on the + next to the "Indiegogo and paypal e-mail adresses, then add the e-mail adress you used to back M3. After this is done, go back to "Campaigns & Perks" to check if you have "my packages" appearing with your backer rank. If all is well, you'll have to scroll up a tiny bit and click on this orange text :
It will take you to a list of every backer level from milestone 3, from there you'll be able to either buy the bike by itself or upgrade your backer level, which also gives you the back along with the upgrade, considering you seem to be a scout, upgrading to deepscanner will cost you 5$ less but still give you the new bike, along with all the extras from deepscanner.
purchase/upgrade buttons should appear there if i'm correct, it doesn't for me as i'm already omni ace and i've already acquired the bike skin.
If you have problems that i wasn't able to help with or that still persist, i'm afraid you'll have to contact support, you'll get help with the issue as soon as possible.