If you haven't looked at Google + recently, you might not have seen the new cover images. The cover image looks* much smaller and the profile image is to the left with an "info card" look, which includes your number of plus ones, your contact info, and your verification badge:
Although it appears that many of the existing cover images have been wiped out by the new cover image:
When I try to click the "change cover" button, it goes nowhere, and I am not able to add a new image. When I look at the page in the G+ dashboard, I do see the cover image:
So, I think the missing cover images will come in at some point, which is why the button doesn't work for now.
*Cover images are still 16x9 (up to 2120px by 1192px), so you don't have to change your image size.
On another note, I have seen quite a bit of this lately:
The dashboard indicates an 85% completion on the page's information. When I click into the Edit Info screen, I see this:
So, if it looks like you need to complete your information, click into edit info to see if that is correct. If it is - complete that info! If not, you're ok.
Check up on the business page within the next few days to see if the image has come in, just in case- don't let it stay with the rainbow default screen.
Local, Social Media and Education Manager