You have Agent for Linux with cPanel/Plesk integration. This Agent is an old build and you want to update it to the new build 22750. You notice that its status briefly changes to Upgrading, then returns to the previous state.
In installation logs, you can find this error:
Mount points of kernel module 'snumbd26' are detected. Unmount them manually, and then repeat the installation.
snumbd26 mount points cannot be unmounted correctly
Reboot the machine and re-attempt update.