nvr hikvision bandwith error

Hello ,

i install an NVR hikvision DS-7604NI-E1/4P/A with 4 cameras cube DS-2CD2410F-IW.
When i add 4th camera nvr appear error message "no enough network bandwidth" .

Then i make firmware update to nvr with the latest version , and firmware update to cameras with the latest version.
I downgrade bitrate to 1024kbps , i downgrade fps , but error message continue.
I make all changes on nvr and one-to-one camera separate but nothing.

Any idea ?

Thanks ..