Thank you for reaching out and providing the helpful screenshot.
The exitcode: 40 error you are seeing indicates that the Nucleus is unable to “unmount” the internal partition where the Roon application is installed. In short, the system is trying to apply the update, but it thinks the storage drive is currently busy or locked, so it safely aborts the process to prevent any issues.
Usually, a simple restart is enough to clear this lock and allow the update to proceed.
Here is what we recommend as a first step:
Reboot the Nucleus: Press the physical power button on the back of the Nucleus once and release it (do not hold it down). Wait for the unit to completely power off.
Wait about 30 seconds, then press the power button again to turn it back on.
Retry the Update: Once the Nucleus has booted up, navigate back to this Web Administration Interface page (192.168.1.110) and try clicking Reinstall or initiating the update via the Roon Remote app again.
Give this a try and let us know if the update goes through successfully. If you still see the exact same error after a reboot, please reply here so we can take a closer look at the health of the internal drive!