thumbnail missing for Facebook and Twitter

Hi,

I am facing issue with missing thumbnail when i am sharing my category page link to facebook or twitter. Problem is only with while sharing category pages. Single Product page thumbnail are showing properly. Tried to solve this issue using facebook debugger. I am getting this error “Inferred Property
The ‘og:image’ property should be explicitly provided, even if a value can be inferred from other tags.”

Please find attached the screenshots.