In your Month View of the Calendar, when you attempt to navigate to the Next or Previous month, you receive a 404 or 200 Error message.
Here are some steps that may solve this problem for you, please go through each one until the issue is resolved:
– Make sure that your Calendar page is set to the right page in the Settings > Viewing Events tab (no need to use shortcode on a page set as the default in the plugin settings)
– Try turning on/off “Strict compatibility content filtering” in Events -> Settings –> Viewing Events.
– Try turning on/off “Use frontend rendering” in Events -> Settings –> Advanced
– Try resetting permalink settings to Plain and then back to your custom style
– This error is most likely a result of a plugin or theme conflict (usually caused by a caching or security plugin).. Please try a different theme temporarily such as Twenty Seventeen, or, disable all plugins and then check if the problem recurrs — then re-enable each one until you find which one caused the problem.