Buttons not showing

Today I installed sharethis 7.0.6 beacause i want to display some social media buttons.

When I use a default WordPress theme the buttons are working fine.
When I use a cutom theme the buttons are not vissible. Is it possible the add the buttons in my page.php in a way the end-user can still make changes in the wordpress settings menu?

Our developement server is not accessable form the outside so I can’t give you an url of the site.

Kind regards
Léon

https://www.ads-software.com/plugins/share-this/