Google recently announced that Google+ will be shut down in April 2019, and access via third-party tools like Jetpack will cease in March 2019.
For now, you can still post to Google+ using existing connections, but you cannot add new connections. The ability to post will be removed in a coming release.
If you had added a Google+ button to your site in the past, you will see a new button, when you are logged in to your admin account. That button will invite you to remove that deprecated service from your site. Your readers, however, won’t see anything.