As a first step, please check the theme system status and make modifications to the WordPress and server parameters mentioned in this guide, if necessary
You could ask your hosting provider to make them for you, as they might have a recommended method in this matter. Insufficient PHP memory and the other parameters have a decisive role in the functionality of the theme and plugins.
If there is still a problem, please deactivate all plugins except theme plugins as a as test, and see if the issue is fixed.
Please let us know the results.