Re-install the SPD USB Drivers, try a different USB port (preferably USB 2.0), or swap the USB cable.

The tool will display various progress stages, such as flashing the system, boot, and recovery partitions.

Install available updates Tap Settings > System > System update > Check for update to check if updates are available. HMD Nokia C31 user guide: Update your phone software - HMD

Some firmware packages, especially OTA (Over-the-Air) updates, can be installed via the phone's stock recovery:

Activate automatic updates in settings to receive official patches seamlessly.

A stable data connection is mandatory. Use a high-quality or OEM Micro-USB cable.

If the device is "dead" or stuck on a logo, you may need to download the full firmware package (PAC or Scatter file). Nokia C31 user guide: Update your phone software - HMD

Make sure your battery is at least 60% full.

Flashing firmware wipes all data. Always back up your photos and contacts first.

Yes – as long as you flashed an official, unmodified stock ROM. Your device will receive future OTAs normally.

This is the used by service centers. It’s safer than SP Flash Tool for Unisoc devices.