Welcome back,
Where is the error displaying? Do you see any errors on your server’s error log? Did you try reverting back to the default WordPress theme and deactivating all plugins other than ours, then attempt to install Event Tickets Plus?
I am unsure what the error you shared with me means and I’m not seeing any logged issues relating to it either. Do you have Event Tickets installed and activated on your site? If not, it is a requirement to run Event Tickets Plus. I also recommend reviewing our New User Primer: Event Tickets & Event Tickets Plus to make sure you are installing and setting up the plugin properly.
Lastly, it appears your System Information didn’t come through properly. Please locate the System Information with me and share it as a private reply.
Thanks and take care 🙂