Error cannot create Categories Folder

[tmyers]

This is on a virtual Windows 2019 server. I have to rebuild existing site, which is working fine, due to joomla upgrades and php updates. I have the site complete less Jdownloads. I had it kind of working but the single category menu items would only work part of the time and it was very slow to load the pages. so I uninstalled it and reinstalled. I even attempted to go back to 4.0.36. to see if that worked better but I am now stuck here. I cannot publish anything at this point due to this error.

I also get this error when I try to check the download area looks like it is attempting to use the Tabulizer helper file? :

All this works fine on the existing site.

  **Downloads Area Check started

Please wait and don't refresh the page or close this window until we are ready!**
**Searching for new Directories**
ClassNotFoundError
HTTP 500 Whoops, looks like something went wrong.
Attempted to load class "JPlugin" from the global namespace.
Did you forget a "use" statement?
Symfony\Component\ErrorHandler\Error\
ClassNotFoundError
in C:\Apache24\htdocs\plugins\content\tabulizercss\tabulizercss.php (line 24)
if(!defined('DS')){define('DS',DIRECTORY_SEPARATOR);}

require_once(JPATH_ROOT.'/administrator/components/com_tabulizer/assets/classes/common/helper.php');

class  plgContentTabulizerCSS extends JPlugin
{
    function __construct(&$subject, $config) {
        parent::__construct($subject, $config);           
        $this->loadLanguage();       
    }

[ColinM]

Hi
Suggest you Uninstall jDowloads but before you do please see article
https://www.jdownloads.net/documentation?view=article&id=253&catid=26

Hopefully when you uninstalled what I assume was jD4.0.46 you did not uninstall the database, the images and the downloadable files. Please advise.
So Uninstall what you have now and re-install the former jD version.

The present challenges may be because the UserGroups database had one item extra in jD 4.0.45 and subsequnent versions.

Soling you original 'challenge' soudnds much simpler!

Colin