Blocking my customers out

That can happen due to a conflict with an e-commerce plugin. Such as a recover abandoned cart plugin or a pop-up checkout plugin. To avoid conflicts, you can enable "Use less restrictive policies (allow AJAX)" in the anti-spam settings. If it doesn't help, you need to check the activity log to determine why WP Cerber identifies legitimate requests as suspicious and blocks them. Once you've figured out the reason, you need to configure exceptions for them. Here is how you can do that: https://wpcerber.com/firewall-http-requests-are-being-blocked/