So had a friend reach out to me that had watched one of my videos that I made some time ago about adding DVR channels to your NVR. He was having some issues adding in his 5116-E1 DVR to his 4232E-E1 and thought there might be an issue where it wouldn't be allowed. After talking with him about the history of his devices I found out that he changed the password for the 5116 a few months after buying it when he bought the 5232 NVR so they would match. So after thinking about things I thought try to use your old password for your DVR if you remember it. Sure enough as soon as he tried the old password he was able to add in the DVRs channels to the NVR..
So something that I thought I would mention as well. If you happen to buy a DVR from someone and they setup the password for the DVR before you got it and you didn't do a factory reset because the seller also provided you the DVRs password and you changed it when you got it. You might want to do a factory reset of the device or look at your devices setup to see if there is a ONVIF user that you can change the password on? Some devices offer this and others don't, normally the Onvif user is the same info as the admin.
So in the case of the 5116-E1 and even my 5108-E1 as well, You can change the Onvif user account to be different from your admin password. So that is good news 1 Lets say that you want to have a different password for your DVR then you have for your NVR. You could setup the ONVIF on the DVR to match your NVRs password. This way if someone that has access to the NVR and was able to pull your password info from like CGI like you can some of the older model NVRs then the password would be the same as your NVR but they still wouldn't have access to all your camera data on your DVR if you setup to only show cameras on the DVR that are already on the NVR.. Just saying..