Fatal error

Our WordPress has been experiencing the following error for some time. Each time we replace the files manually, we fix the error. But new things happen every few minutes, and there’s practically nothing we can do. The WordPress version has been updated to the latest version. But we still have the same problem.

Fatal error: 
Uncaught Error: Call to undefined function nocache_headers() in /home/mainiptv/public_html/wp-admin/admin.php:36 Stack trace: #0 /home/mainiptv/public_html/wp-admin/post-new.php(10): require_once() #1 {main} thrown in /home/mainiptv/public_html/wp-admin/admin.php on line 36

Also, when we update the site manually, the problem is solved. When we want to upload a photo via WordPress, we see this error, and after this error, the site crashes.

IMG Upload Error in WordPress panel :

xgoogle-home-mini-sitting-on-a-window-sill.jpg
An error occurred in the upload. Please try again later.

how can I solve and fix this problem,
please help me,
thanks

• This topic was modified 4 years, 9 months ago by mainiptv.
• This topic was modified 4 years, 9 months ago by mainiptv.