I will include the email that Amazon sent to me today. I have two Amazon Echos. One I bought on QVC and one my daughter bought me on sale on Amazon. I have tried for two days to pair these together with no luck. I did what they said online but I could not set up a Group to create to link them together. You have to make sure they are registered on the Alexa App to do so. My newest one from Amazon would not update after two days. It says to give it two days for updates to take affect. After I created the Group and named it the update was there. Here is the email-you may want to save it. 
I'm sorry to hear that your Echo device isn't downloading the latest software update. Please accept my sincere apologies in this regard.
Before you troubleshoot this issue, you may want to check that other devices (such as tablets or mobile phones) can connect to your Wi-Fi network. If not, you may want to contact your Internet service provider, network administrator, or the person who set up your network for assistance, as your network may be having issues.
After checking your Wi-Fi network for connectivity issues, restart the device to see if this resolves your problems. To restart your Echo device:
1. Unplug the power adapter.
2. Plug the power adapter back in and wait for your Echo device to start up.
If your Echo device still doesn't update, follow these steps:
- Make sure your Echo device is on and has an active Wi-Fi connection. If your device is connected to a Wi-Fi hotspot, disconnect the device from the hotspot and connect it to your home Wi-Fi network.
- Avoid saying anything to Alexa.
- When the update is ready to install, the light ring on Echo device spins blue, and the device installs the latest update. Depending on your Wi-Fi connection, it can take up to over night to install the software update.
Note: Please do not give any commands or use the Echo device while its being updated.
Once the device is updated, please follow the below steps to enable the Alexa multi room music feature.
--> To enable Multi-Room Music in the Alexa app:
1. Select Smart Home from the menu
2. Select the Groups category
3. Select Create Groups to create a group
4. Tap on Multi-Room Music Group
5. Select a pre-set group name from the list, or specify a custom group name by tapping “Create Custom” and entering a name of your choice
6. Tap Next
7. The Alexa app will confirm that it has created your group
Once enabled say “play music downstairs” (if downstairs was your group name) or select your group name from the device dropdown on the now playing screen of the Alexa app to play your music on the selected devices. Please note that you cannot add a device into multiple groups at the same time.
If Alexa does not process your request, and you've used a custom Group name, check that Alexa can understand the name of your devices. For example, if the group name is "b3dr00m" rename it to "Bedroom" For best results, avoid adding special characters to custom group names and use names that have at least two to three syllables. You can rename your group via the Alexa app.
If the issue still persists, please contact us through phone(toll free) or chat for live troubleshooting.
By phone:
https://www.amazon.com/clicktocall-alexasupport
By chat:
https://www.amazon.com/clicktochat-alexachatsupport