I received this Error message in WordPress, to be fair, it isnt my site and I was only asked to look at it for different reasons (setting up Google ads and analytics). Regardless, when I press update to the newer version nothing happens, still the same error and no update. Where do I begin solving this issue? Unfortunately, they dont have a developer they can ask for help, and I`m fairly comfortable with WordPress but never got seemingly two problems at the same time, one being an error message and another WP unable even to update.
Also to note, this same message is on all of the menu pages, so I cannot go and disable a plugin or something like that, it is virtually impossible to use WP at the moment.
Adding error message for easier copypasta:
Fatal error: Uncaught Error: Call to undefined function wp_admin_notice() in /home/sepetys/domains/profline.info/public_html/wp-content/plugins/jetpack/jetpack.php:119 Stack trace: #0 /home/sepetys/domains/profline.info/public_html/wp-includes/class-wp-hook.php(286): jetpack_admin_unsupported_wp_notice(”) #1 /home/sepetys/domains/profline.info/public_html/wp-includes/class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #2 /home/sepetys/domains/profline.info/public_html/wp-includes/plugin.php(453): WP_Hook->do_action(Array) #3 /home/sepetys/domains/profline.info/public_html/wp-admin/admin-header.php(255): do_action(‘admin_notices’) #4 /home/sepetys/domains/profline.info/public_html/wp-admin/update-core.php(594): require_once(‘/home/sepetys/d…’) #5 {main} thrown in /home/sepetys/domains/profline.info/public_html/wp-content/plugins/jetpack/jetpack.php on line 119

1. I tried updating it and clearing the cache looking if it`s an issue with the host servers, but nothing changed whatsoever.
2. This error happened before the update, I don`t have any means to disable Jetpack (this is what potentially caused an issue?)
3. As I understand my client has been told to never update WP to newer versions and its been years since theyve done any work on it.