Twitter's API no longer allow us to query share counts directly. Instead, we rely on TwitCount as a free service that aggregate the data.
Follow the steps below to enable Twitter share counts using TwitCount.
Visit TwitCount and sign up for a free account. Before clicking the button, make sure you are logged into the Twitter account you want to use for your site.
Input the domain for which you want to count shares. For example, entering in verbb.io will report back any URLs shared from verbb.io(opens new window) on Twitter.
Once done, counts will start appearing within 1 hour.