I have an old Core Version - 5.7.5.8 on a Centos6 box running PHP 5.6, and I wish to relocate it to a new server running Centos7 and PHP 7.3. I am pretty sure the old Concrete5 version 5.7.5.8 won't work with PHP 7, so trying to first upgrade the old machine.

On the old machine I backed up the DB and copied the entire folder to another folder, and tried to update it. To get to version 8, it appears I need to first get to 5.7.5.13 (12-16-2016), right? Somehow throw this process, I now get the following error when attempting to access either the front or logon page.

```
An unexpected error occurred.
Class \Concrete\Core\Permission\Key\CategoryTreeNodeKey does not exist
```

I went back to my "copied" backup, but get the same error???

Any recommendations? Thanks!!!