Plugin cannot authorise Gmail

Your WP Mail SMTP Plugin seems to have a Bug just before this line in your doco…

Awesome job! You’ve now successfully connected WP Mail SMTP with the Gmail SMTP settings using the manual API method!

We enter Client ID, Client Secret, Authorised Redirect URI
Then Connect to Google

Google then displays
wpmailsmtp.com wants access to your Google Account

email@gmail.com
This app hasn’t been verified by Google.
If you’re the app developer, you need to submit a request to have this app verified by Google. Otherwise, some of this app’s access to Google user data may be lost. Learn more
When you allow this access, wpmailsmtp.com will be able to

Read, compose, send, and permanently delete all your email from Gmail. Learn more
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Learn why you're not seeing links to wpmailsmtp.com's Privacy Policy or Terms of Service
Review wpmailsmtp.com's Privacy Policy and Terms of Service to understand how wpmailsmtp.com will process and protect your data.
To make changes at any time, go to your Google Account.
Learn how Google helps you share data safely.

BUT there is no Allow or Grant button, only Continue.

When we press Continue, the plugin returns to page
https://.../wp-admin/admin.php?page=wp-mail-smtp-setup-wizard#/step/configure_mailer/gmail

And displays popup
Authorisation Error!
There was an error while processing the authentication request. Please recheck your Client ID and Client Secret and try again.
OK

The plugin does NOT allow us to get to the Google screen where we can Grant permission.

The page I need help with: [log in to see the link]