1. If you have daily backups, I would roll back to before the add-on was installed.
2. I would then try installing the add-on again, in case you missed a step before.
3. If it then still doesn't work, contact the vendor http://www.zen-cart.cn, since they should be able to help you out.
~Sovereign
After I tried to install the multiple admin add-on my admin page went blank giving error 500. So after searching in the forum I found that in CPanel I can find why the error came.
The error was a file that was calling the same thing that was called in another core file. So I deleted it (plus I deleted the whole files that came with the multiple admin addon) and the login page for admin started working. And so the index of admin also is working.
But the problem is every single other pages in the admin area (orders, categories, extra pages, languages,...) they all give a blank page with this error :
HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfil the request.
here's my site just in case:
www.lvleatherwholesale.com
What shall I do? My cart is working fine, it is only the admin part that is not.

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