Missing user psaadm_users for the folder and all the subfolder/files of C:/Program Files (x86)/Plesk/var/locks/
Connect to the server via RDP
Open properties of C:/Program Files (x86)/Plesk/var/locks/ folder mentioned in the error and switch to the Security tab.
Add the username psaadm_users with all the permission as allow:
Click Ok to save.
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