404 Not Found and 403 Forbidden Errors

I really hope someone can help me. My website https://www.2ndchancepaws.com has been down and now it says that it’s not found. The non-secure links show up as Error 403 Forbidden. I have tried everything from deleting the htaccess files, reinstalling WP, adding codes I found in the forum, changing the permissions on all files. Nothing. I believe this resulted from installing the SEO Ultimate Plugin a few days ago and it altered my permalinks, but I’m not positive. I deleted the plugin, but still have the problem. Someone please help!