Plugin Broken Suddenly

This plugin is no longer working properly. I have been using it along with WP Forms and WP Mail SMTP for a while and with the new WordPress update (or something!) it has now stopped working and also causes the WP Mail SMTP plugin to not work. It is creating authentication issues. The error I get is:

Warning: json_decode() expects parameter 1 to be string, array given in /home/shasfyzh/public_html/wp/wp-content/plugins/google-calendar-events/vendor/google/apiclient/src/Google/Auth/OAuth2.php on line 184

Fatal error: Uncaught Google_Auth_Exception: Could not json decode the token in /home/shasfyzh/public_html/wp/wp-content/plugins/google-calendar-events/vendor/google/apiclient/src/Google/Auth/OAuth2.php:186 Stack trace: #0 /home/shasfyzh/public_html/wp/wp-content/plugins/google-calendar-events/vendor/google/apiclient/src/Google/Client.php(218): Google_Auth_OAuth2->setAccessToken(NULL) #1 /home/shasfyzh/public_html/wp/wp-content/plugins/wp-mail-smtp/src/Providers/Gmail/Auth.php(121): Google_Client->setAccessToken(Array) #2 /home/shasfyzh/public_html/wp/wp-content/plugins/wp-mail-smtp/src/Providers/Gmail/Auth.php(53): WPMailSMTP\Providers\Gmail\Auth->get_client() #3 /home/shasfyzh/public_html/wp/wp-content/plugins/wp-mail-smtp/src/Providers/Gmail/Mailer.php(79): WPMailSMTP\Providers\Gmail\Auth->__construct() #4 /home/shasfyzh/public_html/wp/wp-content/plugins/wp-mail-smtp/src/MailCatcher.php(105): WPMailSMTP\Providers\Gmail\Mailer->send() #5 /home/shasfyzh/public_html/wp/wp-includes/pluggable.php(488): WPMailSMTP\MailCatche in /home/shasfyzh/public_html/wp/wp-content/plugins/google-calendar-events/vendor/google/apiclient/src/Google/Auth/OAuth2.php on line 186
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