Something on your site, most likely a highly insecure JoomlaShine template, is broken and tries to save the plugin state in the cache. This is a major security issue and will cause your site to not work properly. Go to your site's backend, Global Configuration and set Caching to OFF as a temporary solution. If you are using a JoomlaShine template contact them and ask for a full refund. They are aware of this major security issue since May 2017 and refuse to fix it. The only solution in this case is using a template from a different provider, preferably one who knows how to write secure code - unlike JoomlaShine.