[Issue]Thumbnail on Main Page / Featured Image / All in One Seo Pack

Yesterday ,Due to heavy load my blog crashed. I inquired from the Hosting company and they told me that some of my plugin is consuming too much resources which is the root cause of the issue and then in the next reply they told me that .htaccess file is creating a sudden resource usage which is taking server down. So they changed the .htaccess file and server resource usage returned to normal.
afterwards while making some changes in wp-config.php [removing WP-Cache Code] I suddenly got database connection error , and I was not sure about the last change so i cannot revert that back , I deleted the wp-config file and then reinstall wordpress to get the database connection.
Here the problem started, Database got connected and blog was live again but on the main page of freshlife theme thumbnail image with post title were not visible . I tried openning post and make them featured again , but when i select the picture and click on Set Feature Image , Pop Up disappears but image doesn’t appear in the featured image section of the page. I tried uploading the new image and then selecting that image as feature image solved the issue but I am worried why already uploaded pictures cant be selected as featured.
All of sudden I have noticed that All In One SEO pack Title tag and Seo Description was missing. I cant figure out what went wrong. Is this something in wp-config.php which is creating all this mess or some database tables got corrupted . I tried installing the theme again to get rid of the issue but of no use , also i tried deactivating all the plugins to see if the issue get resolved but didn’t helped me .
Now looking for the solution on this wordpress forum . Hope so i will get some solution soon.

The blog I need help with is https://www.stayupdated.info.