Unable to update WordPress plugins in Plesk: Update failed: -1

Symptoms

• Unable to update WordPress plugins via WordPress > example.com > Plugins > Update with error:

  Update failed: -1

• Updating the WordPress plugin from WordPress admin dashboard also fails

• Unable to post or update posts via the WordPress admin dashboard

• The plugin Starter Templates is installed and enabled

Cause

Plugin Starter Templates has an issue on their patch notes that acknowledge this:

v3.1.26 – 22-February-2023 – Fix: Plugin installation from WordPress plugins dashboard fails when Starter Template is activated.

Resolution

1. Log into Plesk
2. Disable the Starter Templates plugin from WordPress > example.com > Plugins
3. Update all plugins from WordPress > Plugins > select all plugins > Update
4. Enable Starter Template plugin