You can force the internal software update from the Withings App by going to Devices, tapping the name of your scale and then tapping Check for updates. You can then follow the instructions on screen.
https://support.withings.com/hc/en-us/sections/6212651181969-Smart-Body-Analyzer
https://support.withings.com/hc/en-us/sections/200336167-Maintenance