Hello Foxeh, sorry for the delayed response. I can't offer a solution without knowing a few more details - would you mind mailing service@pushmerchandising.com and letting me know which browser and operating system you were using?
Having the same issue, have tried ordering a sticker and inputted my details on around 6 times and before I can select a delivery option, it goes back to the checkout now page.
Have tried my phone and my tablet, 3 different browsers and they all do the same