Error calling POST

Hi Jason,
I am having trouble getting a Test Email to fire off. (And, any other mail, for that matter.) Your plugin installation and setup went fine, I added the GMAIL API without problems and the Connection Test works fine for port 443. I am using PHP 7 on my server (which may be part of the problem.)

(I do apologize if this thread has already been talked about. I did try to find it in your support threads, with no luck.)

When I hit “Send Test Email” I get this error message:

Error calling POST https://www.googleapis.com/gmail/v1/users/me/messages/send: (400) Precondition check failed.

Below is the Troubleshooting Data:

WordPress: 4.6.1 en_US UTF-8
WordPress Theme: Memberlite – Child Theme
WordPress Plugins: Akismet, Debug, Digital Publications by Supsystic, Download Monitor, Jetpack by WordPress.com, Magee Shortcodes, Memberlite Shortcodes, WP Courseware – Paid Memberships Pro Add On, Paid Memberships Pro, PDF Embedder, Paid Memberships Pro – Address For Free Levels Add On, Paid Memberships Pro – Advanced Levels Page Shortcode Add On, Paid Memberships Pro – Check Levels Add On, Paid Memberships Pro – Custom Post Type Add On, PMPro Customizations, Paid Memberships Pro – Sponsored Members Add On, Paid Memberships Pro – Download Monitor Integration Add On, Paid Memberships Pro – Email Confirmation Add On, Paid Memberships Pro – Email Templates Add On, Paid Memberships Pro – Group Discount Codes Add On, Paid Memberships Pro – MailChimp Add On, Paid Memberships Pro – Pay by Check Add On, Paid Memberships Pro – Register Helper Add On, Paid Memberships Pro – Signup Shortcode, Postman SMTP, Page Builder by SiteOrigin, SiteOrigin CSS, SiteOrigin Widgets Bundle, Theme My Login, UpdraftPlus – Backup/Restore, WP Courseware
WordPress wp_mail Filter(s): wp_staticize_emoji_for_email
WordPress wp_mail_from Filter(s): pmpro_wp_mail_from
WordPress wp_mail_from_name Filter(s): pmpro_wp_mail_from_name
WordPress wp_mail_content_type Filter(s): pmpro_wp_mail_content_type
Postman: 1.7.2
Postman Sender Domain (Envelope|Message): mydomain.com | mydomain.com
//These domains have been changed for this public forum
Postman Prevent Message Sender Override (Email|Name): Yes | Yes
Postman Active Transport: Gmail API (https:oauth2://www.googleapis.com:443)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 0 | 144
Postman TCP Timeout (Connection|Read): 60 | 90
Postman Stealth Mode: Yes
Postman File Locking (Enabled|Temp Dir): No |