How to solve “This version is not compatible with Drupal 7.x and should be replaced” error? Similar to but the solution doesn't work: How to solve &quot;This version is not compatible with Drupal 7.x and should be replaced&quot; error?

I've followed everything I can find but a basic custom theme in sites/all/themes is not working at all. Here is my .info:

name = Custom
description = Custom custom theme built with Stark
package = Core
version = 7.1
core = 7.x

regions[content] = Content
regions[main_nav] = Navigation
regions[sub_nav] = Sub Nav
regions[landing_large] = Front Large Box
regions[landing_ads] = Landing Ads
regions[landing_ad_bottom] = Landing Ad Bottom
regions[landing_books] = Landing Books
regions[home_first] = Home first
regions[home_second] = Home second
regions[home_third] = Home third
regions[search_box] = Search Box
regions[search_ad_box] = Search Ad Box
regions[content_first] = Content First
regions[content_second] = Content Second
regions[content_authors] = Content Third
regions[content_blogs] = Content Fourth
regions[sidebar_right] = Sidebar Right
regions[footer_first] = Footer First
regions[footer_second] = Footer Second
regions[footer_third] = Footer Third
regions[footer_fourth] = Footer Fourth
regions[copyright] = Copyright
regions[shopping_cart] = Shopping Cart

stylesheets[all][] = css/layout.css


I've tried with and without Package, it clearly has defined the version, the core version, the content region...what is it? I copied the .info file from a theme that works perfectly and this is the .info of that other theme verbatim.
Your custom theme is surely not a part of Core package,  so remove that line first. Second, you mentioned that the theme is built based on Stark but you didn't define it in the info file, so add this line :

base theme = stark

Third, usage of version is discouraged in Drupal 7, so delete this line as well.