Since firmware 4.3.5 it's not possible to check for a firmware upgrade for the OC200 from the web interface anymore, if cloud access is not enabled.
Please see this thread and ticket #50219 with regards to this issue.
Technically there is no reason to disable this option when cloud access is not enabled, it seems to be commercially driven. Also, in the changelog in any of the firmware versions there is nothing which shows this change, so it seems it was tried to sneak in.
Please re-enable the option to check for firmware upgrades from the web interface again when cloud access is not enabled.