Wrong password typically means “wrong password”. However, for now let’s put that aside.
You mentioned that your One SL’s keep losing connection. Did you follow the guidelines in the link to set them as surrounds with your Beam. I want to be sure you aren’t Grouping your One SL’s to the Beam. My apologies if you set them up properly as surrounds.
https://support.sonos.com/en-us/article/add-surround-speakers-to-a-sonos-home-theater
Thanks for your reply.
I don't think we should put the wrong password to one side. The password is right as I've used it on all my other devices. The error is wrong.
I set up surrounds using the app. I followed the steps and it all worked, then immediately dropped.
My main concern is why I'm getting a wrong password error, even when I plug in the ethernet. The surrounds will be a breath of fresh air to sort, once I actually get my Beam to work
Are there potentially ‘special characters’ in your password? I’m wondering if there is something beyond the standard defined latin font set, that perhaps the current Unix firmware isn’t properly handling?
Have you called Sonos Support directly to discuss it?
OK...let’s go with your password. Are there any characters such as:
- Capital “I” (eye) and lower case l (L)
- Letter “O” and number 0 (zero)
- Letter “S” and number 5 (five)
- Shift Key was engaged and a special character on the number key was entered instead of a number
Just a few possibilities. If not take @Airgetlam’s advice and contact Sonos Support. Do Not Factory Reset Your Products Again Unless Told To Do So By Sonos
I am having the same issue. I’ve tried connecting to multiple WiFi networks and I get the wrong password error. I’ve had 3 co workers look at the password I have typed in to match what is on the router and they dont see any errors. I just received the Era 300 today.
It’s also telling me wrong password when connecting to a wifi network with no password required.
So, what did Sonos Support say, when you called them directly to discuss it?
@DanNeedsHelp
What device are you using?
Definitely the right password as I copy and paste it from the router settings. Done the same on all other devices in my house and works perfectly. There's no characters or spaces. It's even asking for a password when I plug in the ethernet cable. I gave up on my call to Sonos support as I was on hold for over 50 minutes. That's why I thought I would try the community.
Do your 5Ghz and 2,4Ghz networks share the same name? Could you turn off the 5Ghz network temporarily?
The strange thing is that it won't even connect using ethernet cable. It can't be the internet, as it was all connected before. I did a factory reset and now it won't connect, or even try to connect to the WiFi and when the ethernet cable is in, it's still asking for a password. Before anyone replies thati shouldn't have factory reset, I realise this now, but after reading Sonos help, it did say to do that if your app doesn't connect. Does anyone from Sonos monitor the community and helps?
Rarely, calling support is your best bet
Going through the same issue. Cant get past the wifi connection on my new era 300 surrounds. Getting the “wrong password” error even though it’s 100% correct. Ultra and sub 4 paired flawlessly along with every other sonos product I have. Did a hard reset on everything, attempted to connect on multiple wifi changes, tried hardwire to the router, updated my phone, tried a different device running iOS. Running out of options. Hope there is a resolution to this. I’d really like to get these surrounds working.
Thanks @Masterchri, glad it’s not just me. I feel your pain though as it’s really frustrating and I still have no solution :-(
I’ve been having the same issue with my Sonos Move (1st Gen) since we moved house 5 months ago. My 2x Beam’s and 2x Era 100’s don't have a problem with the new wireless mesh or when I reverted to the old mesh.
Like @DanNeedsHelp I have copy/pasted from the IOS wifi settings and typed the password but still the same error. I have no special characters and no characters that could be confused for numbers, or upper/lowercase letters either. Its as simple as you can get.
I’ve spoken to technical and they tried reset after reset, refreshed the app, used the app on different devices (iPad/Android/iPhone) all with the same error.
They finally gave up and told me to phone in, but with an 80 min wait only to be told the same thing I'm reluctant to waste my time.
I purchased Sonos as it was the best on the market, if expensive, but I am fed up with all the issues since the app was updated.
Any useful help will appreciated.
I am having the exact same problem, have tried resetting everything and it is definitely the right password. I called customer service and they were pretty useless, had me run through the generic stuff before saying it was my internet providers fault even though all the settings are as they recommend.
looks like I may have found a solution! try uninstalling the app from your phone and reinstalling!
Seen other topics suggesting a “force close” to clear up Android App issues.
I had the same issue trying to setup my two symfonisk speakers, one used before and one new, in a completely new setting. Fixed it by uninstalling and reinstalling the app on my phone.
None of the above worked 
tried ethernet cable, reinstalled the app, rebooted router and other efforts but nothing. I now have three speakers which are expensive junk. Think it's time to get a Bose or Samsung soundbar.
Or maybe call Sonos Support directly to discuss it?
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
I'll try the helpline again when I have an hour plus to be on hold. Shame they don't help in the community chats like other companies 
