I have a site that was upgraded from Drupal 6 to 7 and now it is finally Drupal 8.1.1 But there are some strange problems.
1) I put the site offline, and now I can't go back online. I get the following error message:
Fatal error: Cannot instantiate interface Drupal\Core\Cache\CacheBackendInterface in /home/mysitename/public_html/core/lib/Drupal/Component/DependencyInjection/Container.php on line 268
2) status report gives me the following problems: