Moved Site and Plugin Started Throwing Errors

Hi, I hope this forum is still being monitored. I recently moved this site, https://www.synergytheater.com/, from one host to another. The plugin still shows that we’re connected to Vertical Response, but I’ve had to deactivate the plugin because the site was displaying huge error messages across the top of every page when it was activated:

Warning: count(): Parameter must be an array or an object that implements Countable in /home/customer/www/synergytheater.com/public_html/wp-content/plugins/deluxe-marketing-suite/classes/class-dms-public.php on line 87

The other message that was displaying on the plugin screen when the plugin was activated was this:

The plugin generated 258 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

Do you have any direction for me on this?

Thanks,
Lisa

The page I need help with: [log in to see the link]