Email not sending

Using Updraft with WP Mail SMTP, connected to Gmail. Normal messages from the site work correctly.

I see the following after completing a backup, with email notification turned on:

Sending email (‘Files and database (Full backup)’) report (attachments: 0, size: 0 KB) to: info@…
0134.075 (0) PHP event: code E_WARNING: json_decode() expects parameter 1 to be string, array given (line 177, wp-content/plugins/updraftplus/includes/Google/Auth/OAuth2.php)
0134.094 (0) Exception occurred when sending mail (Google_Auth_Exception): Could not json decode the token
0134.094 (0) The backup apparently succeeded and is now complete

The message that was trying to be sent’s JSON looks like this:

“mail_id”: “13”,
“timestamp”: “2020-04-30 14:03:27”,
“host”: “(IP address deleted)”,
“receiver”: “(email address deleted)”,
“subject”: “Backed up: Wai\u02bbalae Iki … (UpdraftPlus 1.16.23) 2020-04-30 14:03”,
“message”: “Backup of: https:\/\(hostname)\r\nUpdraftPlus WordPress backup is complete.\r\nBackup contains: Files and database (Full backup)\r\nLatest status: The backup apparently succeeded and is now complete\r\n\r\nEmail reports created by UpdraftPlus (free edition) bring you the latest UpdraftPlus.com news – read more at https:\/\/updraftplus.com\/news\/\r\n\r\n* Clones have just got bigger (22 April 2020)\r\n* Working from home: What we can learn from WordPress bloggers (17 April 2020)\r\n* How has your business and WordPress site been affected by the Covid-19 crisis? (10 April 2020)\r\n* Top 5 tips to keep active and healthy during lock-down (7 April 2020)\r\n* WordPress community: Helping to provide services online for people in isolation (24 March 2020)\r\n* How to Backup a WordPress Site: Step by Step Guide (6 March 2020)\r\n\r\n\r\nLike UpdraftPlus and can spare one minute?: Please help UpdraftPlus by giving a positive review at wordpress.org. Review UpdraftPlus – https:\/\/wordpress.org\/support\/plugin\/updraftplus\/reviews\/?rate=5#new-post\r\n\r\n”,
“headers”: “X-UpdraftPlus-Backup-ID: 333fedfd4d29”,
“attachments”: “”,
“error”: “”,
“plugin_version”: “1.9.5”
}

Thanks!