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Error 7 means 'login error.' Some failure to authenticate your access has happened.
This may be, simply, because the DVR or other device at the other end is not currently in a state to accept logins: not connected to internet, not fully initialized, etc.
Or, because some element or one device along the link from you (trying to log in) to the remote device (trying to authenticate your access to it), is 'down', not functioning, not communicating.
Make sure that, wherever you are now, you have full internet access, and all devices at your current location are in good condition... a power outage may damage or disrupt devices and their performance. For a good condition of initialization, it is well to power all local devices Off, leave them all that way for a good 10 minutes or more, then when you power them up, power them up one at a time, with the 'source' devices (the ones that provide the connection or data) powered On first, and given some time (a minute to five minutes) to initialize first.