Hikvision DVR offline after it restarts

I recently brought Hikvision DS-7A08HGHI-F1 ECO 8CH DVR, I have issues with net connection after each restart of the device. I could bale to connect to the net with all configurations setups at Network-Platform access tabs, but when the DVR restarts (due to power cuts) it automatically goes to offline. I use Tenda router to connect to the net with DVR. Kindly help me to fix this issue