Wordpress can require what’s called a “manual” update for a number of reason, from being too old of a version, php version related, corrupted files, missing files etc.

You can find the latest release, as of this date, 5.6.1 here https://wordpress.org/download/releases/

The steps wordpress provides are as follows: https://wordpress.org/support/article/updating-wordpress/#manual-update

Screenshots showing the process will be attached as well.

Step 1: Replace WordPress Files

1.       Get the latest WordPress zip (or tar.gz) file.

2.       Unpack the zip file that you downloaded.

Create a folder somewhere you can find it easily.

3.       Deactivate plugins. (if you are not able to get into wp-admin for any reason, you can skip this step for now, or “disable” them by renaming the wp-content\plugins folder to plugins1, that will also disable them, renaming it back will make it load them up again).

4.       Delete the old wp-includes and wp-admin directories on your web host (through your FTP). You can use https://www.brinkster.com/KB/Article~KBA-01063-Z5H1R6~How-do-I-connect-to-my-Windows-ftp-site if you are unfamiliar with FTP, you will need it for the next step to upload the files.

5.       Using FTP or your shell access, upload the new wp-includes and wp-admin directories to your web host, in place of the previously deleted directories.

6.       Upload the individual files from the new wp-content folder to your existing wp-content folder, overwriting existing files. Do NOT delete your existing wp-content folder. Do NOT delete any files or folders in your existing wp-content directory (except for the one being overwritten by new files).  Most of the time, you can simply skip this folder. We would recommend NOT messing with it as the wp-content is where any themes, plugins, uploads and configurations reside, so messing with them can break the site, see screenshot below.

7.       Upload all new loose files from the root directory of the new version to your existing WordPress root directory. Here we select all, then ctrl click the wp-content and wp-config.sample.php file so NOT upload them, which just does the core wordpress files

Next step once it finishes uploading is to visit yoursite.com/wp-admin  It should prompt for a message similar to this, simply hit update WordPress Database to continue:

If you had disabled any plugins, you can go re-enable them now, we would recommend updating them as well.