Form giving SPAM error after recent update

I’ve had this widget on a client’s site for awhile and after updating it about a week ago the form now flags emails as SPAM when someone attempts to use it. Has anybody else experienced this?

UPDATE: I uninstalled the plugin and when I tried to activate it after reinstalling it, it says The plugin does not have a valid header.

https://www.ads-software.com/plugins/constant-contact-signup-form-widget/