It should be common information update at this point on the internet that there is an incompatible jump between Concrete5.6 to Concrete5.7 For about 5 years you could just hit upgrade and go from 5.1 to 5.2 to 5.3 etc all the way to 5.6.x.
Then Concrete CMS community released “Version 7” in year 2014, which was a fairly deep code rewritten to modern PHP standards and it was a incompatible jump from versin 5.6 to versin 5.7 and you could not update your concrete cms website with just click of a button.
To ease the process of upgrade from version 5.6 to new version 7 The Concrete CMS community also built migration tools, but it was really about creating a new site and pulling the old content into it. Since then Concrete CMS community have left the number “5” from version number and with the release of version 7 concrete cms community again kept the magic update button working just fine for all the versions thereafter from version 7 to version latest concrete cms version.
All this activity (version incompatibility jump) took place in 2014 /2015. Concrete CMS community promised at the time that they would continue to initially support version 6 for security reasons. Concrete CMS community knew that major websites were built with version 6 and it will take time to find a consistent strategy to restore your website. August 2th , 2019 Concrete CMS community officially announced the end of life of version 5.6
You may have noticed that all of version 6 plugins were free for a while ago. Because it doesn’t make sense to sell extensions for a product Concrete CMS community don’t support, Concrete CMS community stop selling the old marketplace after three months on November 22, 2018.
It’s actually been over 3 years since Concrete CMS community deleted version 5 of Concrete CMS official website and stopped providing support to it.