Our plugin needs to find matching domain names in Wordpress and Unbounce in order to authorize the connection. Luckily, if you're running into this issue it's usually a super easy fix.
The biggest reason you might not be able to Authorize with Unbounce is because the domain you've added into Unbounce doesn't match the 'www' part of the URL that you have in Wordpress.
If your Wordpress is installed without using the 'www', then simply edit your Wordpress domain in Unbounce (remove the 'www.' part of the domain). Then go back to Wordpress and try to Authorize the plugin again.
If you've ensured everything matches but you're still running into issues with our Wordpress plugin, have a look at our documentation about "Troubleshooting WordPress Plugin Technical Issues", or contact our support team.