When pressing sync butting in order to add the doorbell in the app, there is no sound.
The doorbell keeps blinking red/blue. What does that mean?
Is the battery low?
Even when charging, the light keeps blinking red/blue. Is this normal?
I tried resetting and to turn power off but the light keeps blinking red/blue.
I have trouble finding answers to my questions in dutch.
I hope someone can help me.
If you look at the Help section of the Eufy app, it says that a red/blue blinking LED means that doorbell chime is being updated. Once the chime starts updating, the doorbell won’t add until the update has finished. I would check the chime and see what the LED shows on it. Maybe unplug the chime and see if the doorbell will add.
Thanks for your reply 
It is the doorbell that is blinking, not the chime.
I suspect I interrupted the firmware update process.
I think there is nothing I can do but wait until the battery is empty and hopefully it will start again and will the firmware be installed correctly.
Have you tried the reset? There is a hole in the back of the doorbell that will let you use the supplied Sim tool to reset the device. That should restore it to factory settings. I think you have to hold the tool in for 10 seconds for a full reset. You will have to add it again afer that. Make sure you leave it powered up for a while after adding it and it should update itself.
I’ve got the same probleem.
We’re you ever able to fix the issue?