@Oceani5: Sorry it’s not working good. But I need your site URL to check in what are you doing in.
1. About the slider, which slider type are you using it. If you are using Page or Post or Category Slider then you need to have featured image in those pages/posts. It’s not enough to just add image. See this for featured image http://catchthemes.com/blog/videos-blog/video-series-adding-featured-image-wordpress-postpage/
2. About the image size, I am but confused and I need to check in your site first.
You can check our theme instruction page at http://catchthemes.com/theme-instructions/catch-everest-pro/ where you can read about Image Sizes and Content Featured Images.
Image Sizes
Feature Post Slider
Width: 1140px
Height: 450px
Thumbnail in Homepage and Archive Page
Width: 690px
Height: 462px
Small Thumbnail
Width: 390px
Height: 261px
Content Featured Image
You can select the content featured image sizes options from “Appearance => Theme Options => Content Featured Image Options”.
Note: If you are doing all this correctly, there there might be changes of plugin conflict. So, check by deactivating recently updates/added plugin one by one.
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