Hi,
many thanks for your request. Pls can you check which config files are available on your WireGuard directory.
ls -la /etc/wireguard/
At least you should have 1 client file wg0-client.conf
In addition the WireGuard user guide from DietPi side https://dietpi.com/forum/t/dietpi-software-details-for-all-installation-options/22/127