My theme and fv flowplayer plugin have issue

I’m using fv flowplayer plugin pro version.

But I found one problem, that is I can’t set featured images in my wordpress pages.

When I set featured image, an unknown blank image had already selected and it can’t be changed.

I’ve checked all pulgins one by one, as the results I found that problem is between my theme and fv player .

I’m using Guru theme (https://themeforest.net/item/guru-learning-management-wordpress-theme/7807232)

and I found out a similar issue in this forum. Theme may be different. (https://foliovision.com/support/fv-wordpress-flowplayer/troubleshooting/my-theme-lms-and-your-fv-flowplayer-plugin-have-issue)

Please fix this problem. Thank you.