Whonix 15 has reached EOL (end-of-life). If you have not already done so, we strongly recommend upgrading your Whonix 15 templates and standalones to Whonix 16 immediately. The Whonix Project provides fresh Whonix 16 template packages through the Qubes community template repositories, which you can install in dom0 by following the standard installation instructions. Alternatively, the Whonix Project also provides step-by-step instructions for performing an in-place upgrade of an existing Whonix 15 template. After upgrading your templates, please remember to switch all qubes that were using the old template to use the new one.
For a complete list of template releases supported for your specific Qubes release, please see our supported template releases.