Symptoms
The installation of a WordPress instance stuck on Downloading and Unpacking:

The following errors can be found in the
/var/log/plesk/panel.logwith enabled debug:DEBUG [extension/wp-toolkit] Downloading of WordPress 5.4 package will performed at 3 attempts.
DEBUG [extension/wp-toolkit] Start attempt 1 to download package using URL: https://wordpress.org/wordpress-5.4.zip
INFO [extension/wp-toolkit] Acquire lock 'download_package_wordpress-5.4.zip'
Cause
Because of the network issues (WP Toolkit could not download the package due to low speed), the necessary WordPress installation package can not be downloaded.
Resolution
For Linux
Connect to the server via SSH
Download the package manually using any method
Move the package to
/usr/local/psa/var/modules/wp-toolkit/packages/and changed the ownership to the correct one:# mv wordpress-5.4.zip /usr/local/psa/var/modules/wp-toolkit/packages/wordpress-5.4.zip
# chown psaadm:psaadm /usr/local/psa/var/modules/wp-toolkit/packages/wordpress-5.4.zip
Remove the "lock" files:
# rm -rf /usr/local/psa/var/modules/wp-toolkit/locks/*
For Windows
Connect to the server via RDP
Download the package manually using any method
Move the package to %plesk_dir%varmoduleswp-toolkitpackages
Remove the "lock" files under %plesk_dir%varmoduleswp-toolkitlocks