Hi, @kadamczyk !
Julie here from Shopify Support.
Which theme are you using? Some themes offer you the ability to choose a social media image for your online store directly through the theme editor in Online store > Theme > Customize > Theme settings. If your theme offers this option, then the social media image you choose in your theme settings will override any social sharing image settings from Online store > Preferences.
Do you see an option to add a social media sharing image there? If so, then you will need to add the social media image through the theme editor.
However, if your theme does not offer the option through the theme editor, then it sounds like you may need to use the Facebook Sharing Debugger to refresh the information that is saved for your page links. Typically, it will take Facebook a few days to update this information, but the Facebook Sharing Debugger should speed up the process.
I hope this helps. Feel free to respond here and let me know which theme you’re using and whether the Facebook Sharing Debugger does the trick.