You could try rebooting your wireless router(s). I had this same issue and tried all the suggested items such as unplugging Echo Dots for 1 min, deleting group and recreating, uninstalling and reinstalling Alexa app, etc. None of that worked until I rebooted my router and then I was able to add all three to the group. I spoke with a service rep at Amazon and they helped patiently troubleshoot, as they knew we should be able to do it.
I have the same issue with my new echo device (living room). If I create a Multi-Room Music Group, the new device is not reachable as soon as I select one of the previous devices, if I select the new device (living room) then all the previously owned devices are not reachable... I rebooted the wi-fi router, same result.
This is what I call a bug !
I have rebooted the wi-fi router
I have deleted and recreated the Multi-Room Music Group.
I am having the exact same issue and I do not use Google wifi or a mesh system. When I first set up my echos I was able to create the multi room group just as required. This lasted for a day and then stopped working. I have spent a lot of time on the phone with Amazon to no avail. I had already tried all the probable fixes before calling support and tried them all again with their guidance. No change. UPDATE: I finally found a fix by putting one echo on the 2.4g network and the other on 5g. This should not work according to Amazon, but...
I am having the very same issue. I bought the new echo sub and was, after a day or so frustration, able to get the new sub to join my "everywhere" group. After that was successful I tried to add another echo dot to that everywhere group but it came up as "device unreachable". I tried rebooting the new dot. Nothing. I tried removing one other dot from the everywhere group thinking maybe I had reached a maximum. Still unreachable BUT now the dot I removed from the preexisting group was also unreachable! I tried rebooting my Xfinity X1 router AND the new dot and it's still unreachable, both of them. I am so frustrated with this I'm almost ready to throw them out on the ice for hockey practice. Please help!!
UPDATE SAME DAY!!: After submitting the above issue I decided to go back into my Alexa App and delete my existing "everywhere" group. I was afraid that it might screw up my new Sub + 2 echo stereo but was at my whit's end. IT WORKED!!! I now have every echo, sub, and dot that I want back on the everywhere group and it is blasting as I type here. I am a happy camper now! Thanks for your help!! Sometimes it just takes doing the absolute obvious to get to where you need to be. OO RAH!!
I had the same problem, I had a new Echo that I tried to pair with a speaker multi-room group and got Unreachable, I fix it by deleting the group and recreating it. That simple....Just took me 3 weeks to find the answers here LOL.
Just got 2 of the Echo Plus' and having the same issue. All are on the same wireless network however creating a group, I had different "unreachables" appear. I already have a Dot and Echo, so that's 4 altogether. Tried creating a couple different groups (Upstairs, Downstairs and Everywhere). Echo and Echo plus downstairs, Dot and 2nd Echo Plus upstairs. Sometimes I have 3 out of 4 available, sometimes 1 out of 4. Seems when I have 2 of the new Echos as part of the same group, one is unreachable. Still going to experiment a little...
UPDATE: Might have the solution for some of you...
Using the Amazon App on my phone, I looked at each of my devices and found that one of the new Echo 2nd Gen. devices had an older software version than the other, which seems to explain why that older one would show as "device unreachable". I checked this site:
which had the latest software versions for many devices. The instructions had me mute the older one until it does an update (I tried the voice command to check for updates and it did not "have that ability" or something like that). Anyway, if you mute the device for a period of time, it's supposed to do an update. We'll see if this works. Check all of your devices also for the latest software version.
UPDATEv2: The update worked. No issues with groups. Check the link above and see what your versions are on your devices.
My devices have just started to experience the same problem. I have been using my echo dot and echo as multi-room speakers for months without a problem. I have tried removing them from my wi-fi and rejoining them - they are both on the same 5ghz connection. I have tried resetting them completely with no success. Really frustrating as we have a party New Year and really want them to be working again for this! If anyone has a resolution please can they post here? Thank you
I have had this issue before. Because the Echo's use WiFi device that they are directly connected for communicate with each other, having them connected to a multi-access point network across multiple access points doesn't seem to work.