I just cleared my cookies and logged in and the 60k offer no longer reverts to the 40k one. I think I found the trick to get the 60k offers if you have miles in your account. Click apply now on the 40k offer and enter your mileageplus number and pin and let the application open. Close the application and open united.com once again and click on the credit card offer again in the home page. It should now go to the 60k offer.