Reolink 8ch NVR (12 Channels show)

[harry_517268510953683]

Got Reolink 8ch NVR and when setting it up it has 12 channels showing on the channel page. Hardwired 6 into the back of the NVR and have 6 connected to a POE switch. Started to add the poe switch ones onto the nvr via the channel tab and got to the 10th one and it said I had to delete one before I could add another. Why is this?? If I shows 12 channels why can't I use them all. If I had know this I wouldn't have gone a bought an extra 4 cameras. Any info here would be great.