Hello.
Please recheck your error.log in your server configuration, about any relative errors. If you can not find error.log file, please contact support of your hosting company about helping in finding this file.
Otherwise probably, its because of conflict with some other plugin or actual theme.
Please try to deactivate one by one all your active plugins at the WordPress > Plugins menu and make testing after each plugin deactivation.
If its not help, please deactivate all your plugins and active the default WordPress theme. And then retest it again.
We just need to find the reason of this issue.
Kind Regards. .
