It is nearly 100% certainly not related to the theme.
But to test that, switch to a different theme (e.g., TwentySixteen), and see if the image uploading works. It won’t if it doesn’t now.
If for some reason I can’t fathom at the moment allows you to upload images to the media library, then try uninstalling Weaver Xtreme, then re-installing in. Something may have been corrupted on your installation. Try re-installing WordPress from the Updates menu as well.
If none of these work, then it almost certainly is a hosting issue.