The plugin authors seem to be getting forceful about making people register with their cloud platform.
On a similar plugin (Eventbrite Tickets Add-on) and (The Events Calendar) plugin, in general, they got rid of the legacy imports option to make people use their API importer.
If the plugin works as intended (4.7.5) and shows the error messages you are fine though. Just use a plugin like (Wp Hide Plugin Warning and Error Messages). Most paid plugins you use without a license will show an error but will work fine.