Upgrade Link Showing Page Not Found (404)

Dear Friends

We are facing new born issue in our wordpress theme right now. “An updated version of WordPress is available”

“You can update to WordPress 5.4.2 automatically:”

Whenever we click on update now then
“/wp-admin/update-core.php?action=do-core-upgrade” and show page not found or 404 error.

We have tried many time but receiving same issue from update section.

• This topic was modified 4 years, 8 months ago by Jan Dembowski.
• This topic was modified 4 years, 8 months ago by Jan Dembowski.

The page I need help with: [log in to see the link]