Appointments+ - WP Dashboard Alert - Curl Not Installed

Greetings! I hope you're doing well today.

Here's what the alert says: "[Appointments+] Either php curl is not installed or HTTPS wrappers are not enabled. Login with Google+ will not work. "

I checked with the Bluehost tech support about having 'allow_url_fopen = On', and they confirmed Curl is active on my server. What else could cause this alert?