I too, had the problem of not being able to access the admin page after the update. There was a period of time, early on, when my site was only http. Then I changed to https. Accordingly, some image links were only to http. After I disabled the update to get to the admin page, many images appeared only as place holders, some came and went, and the site, with respect to images, was pretty messed-up. I have just now manually fixed my images to point to https and the site is working again.
Afraid to update to the newer version of the plugin in case it doesn't work or creates new problems for me. Anybody else with same problem who has test drove the 3.1.1?