Hello!
First off, thank you for your purchase and welcome to our premium plugin support forums! Can you please describe what happens when you select the “Schedule multiple events” button? Does it allow you to add your desired time/date settings, but won’t save when attempting to publish/update an event?
I see you checked ‘Yes’ to reverting back to the default WordPress theme and deactivating all plugins other than ours as instructed in the Testing for conflicts guide, but can you please confirm this?
Would you mind testing again, ensuring WP_DEBUG and WP_DEBUG_LOG are enabled on your site’s wp-config.php file. Any errors will display at the top of your page as you try to reproduce the conflict. I also recommend right-clicking your mouse and opening the ‘Inspect’ tool to see if any errors display in the console. Note what you find and please include it in your reply.
Thanks again and have a great rest of your day. Cheers!