I had the same problem. The outdoor station was working. I can see the video image on the indoor station and the hik-connect app. But when I ring the doorbell a female voice says "calling failed".
Also I couldn't change any settings on the outdoor station because it kept saying "incorrect password". I believe the mistake I made was upgrading to the wrong firmware. Hikvision makes different firmware versions for different country's. I used the uk firmware. Eventhough I live in the Netherlands. This was my mistake.
What I did to solve the problem:
I went to the dutch (Netherlands) website of hikvision hikvision.com/nl.
I searched for DS-KIS702.
Scrolled all the way down. Downloaded the:
Upgraded the firmware of the
DS-KH6320-WTE2 with the SADP or BATCH program from Hikvision.
Upgrading the
DS-KD8003-IME2 was more difficult because of the incorrect password problem. But I found this program called
TFTP. With this I could change the firmware.
With the correct firmware my old password for the
DS-KD8003-IME2 was the correct password again!
I rang the doorbell (with my fingers crossed) but still I got the "calling failed" message.
I used the indoor station next. Went to the configuration menu to reset the device using the "remove all" option. After the device restarted I entered the new password. (I used the old password which worked to enter the
DS-KD8003-IME2, don't know if this matters).
I used the wizard to configure the device.
Rang the doorbell again (fingers crossed) , and YES finally the indoor station was ringing again. After a whole week of struggling.
I believe that maybe the password of the indoor station needs to be the same as the outdoor station.
In the release notes of the uk firmare it says:
When configuring the video intercom system, the registration password of the door station
must be configured first, the registration password on the indoor station must be the same as the
door station to register successfully.
In the release notes of the dutch firmware it doesn't mention this.
Anyway, I hope you can use this information to solve your problem.