Site Preview button leads to “Error: Invalid URL was requested.” being showed in Plesk UI

Symptoms

• The Site Preview button displays an error instead of showing site content:

  Invalid URL was requested.

• Server OS is Ubuntu 20.04 or 22.04.

• Manually replacing http by https in the preview link does make the site preview content to be displayed.

• There is no location ^~ /plesk-site-preview/ directive under listen IP_ADDRESS:443 ssl in /etc/nginx/plesk.conf.d/server.conf:

  # grep "location ^~ /plesk-site-preview/" /etc/nginx/plesk.conf.d/server.conf
  #

Cause

This is the Plesk bug PPPM-14141 which will be solved in future Plesk updates.

Resolution

Until the bug be fixed, as workaround:

1. Log in to Plesk via https://<server-IP-or-hostname>:8443, e.g. https://203.0.113.2:8443.
2. Navigate to Tools & Settings > Customize Plesk URL
3. Select No custom URLs. Only https://<server-IP-or-hostname>:8443
4. Save the changes