If your Facebook share counter is not showing probably you should update your settings. Here is what you need to do.
Ensure that your counter update period is not frequent. We recommend 6 hours, but you can choose your own too (too small a period may lead to miss share counter updates).
Increase the period of counter update for the older posts. Usually, those posts do not require so frequent counter extraction. Because Facebook API limits the calls per hour that will save spots for updating your most frequent posts
Ensure that you have set the token inside the settings for reading the share values. The Facebook counter you can get from the Facebook API or using SharedCount API.