If the router displays a Header Mismatch or Validation error, verify that the software file matches the modem module. LP2 and LP3 software can be used only on European modems, while LP and LE software applies only to the MC200 series modules.
If the router displays an error indicating that an upgrade process is already running, it is likely that it has not yet finished or had to abort an earlier modem or router update. Wait for any updates to finish. If there aren't any upgrades running, reboot the router and try again.