Fatal error: Call to undefined function run_system_check() in head.php line 49

[tradeniti]

Dear sir,

i have uploaded admin folder in my ftp server /htdocs/admin from the latest abantecart 1.2.4.
withing a second my admin panel stopped working and showingerror  message :

Fatal error: Call to undefined function run_system_check() in /home/vol3_5/HOSTINGSITENAME.com/MYUSERNAME/htdocs/admin/controller/common/head.php on line 49

i have tried replacing the old system by again uploading the "admin" folder.

i am not a coder and i dont know anything about php and all this kind of stuff. but is explained simply i can do my best to fix it.
my site [frontend] is working pritty will [front pages and all site] only problem is with admin and backend of abantecart.
i am currnty on abantecart 1.2.1

please help me. and thank you so much for your time to help me.

[Basara]

If you trying to upgrade it is not enough to just upload files.
Your need to upgrade database too and you can not jump from 1.2.1 to 1.2.4
Please upgrade successively from 1.2.1 to 1.2.2 -> 1.2.3 and then to 1.2.4
http://docs.abantecart.com/pages/upgrade/auto.html

[tradeniti]

Dear Basara,
Thank you for your replay. i was not aware about this information. now my backend is stopped working.. is thare any way to start it again?

or i have to install a fresh copy of abantecart ??

[Basara]

Restore backup or install fresh copy