Ok- so Arc was not ethernet tied- Amp was- once I put the ARC on ethernet as well- worked perfectly- for those who may also have this issue- is there a rhyme or reason?

Did you use the “disable WiFi” option?

That is a  longstanding dirty trick by the Sonos developers as it does disable WiFi but by turning off the entire radio. So No WiFi, no SonosNet, no Surround links. If they can’t see changing the wording at least they could add a warning message.

Should I use the disable Wifi option? Because update- the next day, I had two more AMPs installed and wired into the Eero and then the initial amp which was used for surround sound stopped working… so now I am trying to figure out how to recorrect the problem. It looks like they only used one ethernet cord  for the 3 AMPs and spliced it into the EERO so should I try to use a direct ethernet for the surround AMP?

There are very few situations you should disable the Sonos radio. You would want to consult with Sonos support first to make sure that the radio being on is your issue.

I have no idea how one would splice an Ethernet link for multiple devices, I don’t even think it is possible.

You didn’t answer the basic question I asked above so any further help is going to be wild guesses.

Can you confirm how you’ve connected them? You can only pair similar speakers. If you group rooms they’ll play the same source. If you bond speakers to a master you’ve set up surrounds to your Arc. 

No, don’t disable WiFi.

If you play a music source in the surround room does AMP play?

Ethernet splitter-guessing this is being used as there are three new amps and only one new Ethernet attached directly to my eero. https://www.bestbuy.com/site/insignia-2-line-phone-cord-splitter-white/6406531.p?skuId=6406531&extStoreId=254&utm_source=feed&ref=212&loc=emergingcategories&gad_source=1&gbraid=0AAAAAD-ORIiHMee6Fu17MKWvn8gyF6M4y&gclid=Cj0KCQjw2uiwBhCXARIsACMvIU37F6gMct6oo3coLx-nKzmzNJwt5yWiPm3RMWTAA6ptFEC01KsgSYUaAmFxEALw_wcB&gclsrc=aw.ds

apologies on missing your basic question- WiFi is Not disabled. With using Ethernet should it be? 
obviously in this chat I see differing opinions on this already 

Not grouping rooms together- bonding the amp to the arc like my sub already is (previously had one sl pairs for surround) via the app as surrounds. That went through “successfully” though clearly not playing. 

That is a phone splitter, it will not split Ethernet which uses the wires very differently than a phone connection. It should be removed as it is likely causing problems.

If you want to “split” Ethernet you need a Switch, around $20 for a decent one. Check the Sonos Incompatible Hardware list before buying anything.

https://support.sonos.com/en-us/article/incompatible-network-hardware

Switch: https://www.amazon.com/gp/product/B00A121WN6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Do not disable WiFi without consulting Sonos Support.

WiFi enabled or disabled is really simple to decide if you can see the internal Sonos data (you can’t) and understand how to get surrounds/Subs to work with WiFi disabled.

I read no advice to disable the WiFi on any Sonos without consulting Sonos. Some of the symptoms you describe could be caused by you disabling WiFi, so it was asked if you did.

You should not use a phone splitter to splice an ethernet connection because al information on an ethernet (or the internet) is cut up in small packets that are addressed to a recipient. This was once explained to me as follows:  each recipient on an ethernet has it’s own address. Since you can’t have two recipients on one address you need a extra postmaster conveying packets to the right address if you use one cable for more than one device. An ethernet switch is the extra postmaster.

WiFi is not disabled and a phone splitter is not being used. I was traveling yesterday and half assed tried to search for the Ethernet switch.