If you select 'Check online update', You must stay this activity until to finish download.
If you close ODROID Utility, You will fail to update.
Open browser and download updatepackage-odroidc2-eng-s905_5.1.1_master-xxx.zip
Run ODROID Utility and select menu 'Package install from storage.'
Select 'File Manager'
Select 'Download/updatepackage-odroidc2-eng-s905_5.1.1_master-xxx.zip'
Wait a second and click 'Proceed'
