Ensure you verified your email and confirm your Ads Manager is not suspended. For more information, please see Why was my advertising account suspended?.
Having an ad blocker on may also prevent you from starting campaigns. Ad blockers tend to cause troubles not only in our Ads Manager but also in those of other ad platforms as well. For some advertisers, ad blockers may result in an "Error" or a "Your ad has 11 errors" message in the Ads Manager.
Please turn off your ad-blocker and refresh your page. If you have browser extensions, check to make sure they do not have built in ad-blockers. You should see the "New Campaign" button in the upper right corner of your screen at all times.
If you continue to run into issues, please contact us and include screenshots of any messages that appear on your screen.