Huh? I’m confused, Sonos doesn’t offer support for Power over Ethernet. 

Normally speaking, you would install the two Era 100s as separate rooms, then use the controller option to add them as surrounds for your Sonos soundbar. 

I beg your pardon, I missed the ‘Pro’ part of your post. 

Yours is the first question I’ve seen about the new ‘Pro’ model, your installer should have had instructions. But once they’re powered, they should be connected by the method I’ve suggested. Unfortunately, I don’t have any experience with PoE to answer that part of your question. I’d be tempted to temporarily plug them in to the power to get them set up, and then work on the PoE aspect. 

I’d also be checking the various downloads on the sales page at https://www.sonos.com/en-us/shop/era-100-pro

There is an odd detail in the product documentation:

Can I use Era 100 Pro as rear speakers in a Sonos home theater system?

Yes. If the Era 100 Pros are using a wired network connection, then the home theater primary (soundbar or Sonos Amp) must also be wired to Ethernet. If the Era 100 Pros are using their backup wireless network, then the home theater primary can be wired or wireless.

I know nothing about the Pro systems, but from this it sounds like the Pro setups are wired by preference, with a  “backup wireless network” alternative. Odd that Sonos feels wired is a more robust setup, but drop default Ethernet connection in the latest hardware in the standard range - it’s an optional extra for the Eras. 

I was hopefully to be able to keep the wired connection for power and somehow adjust the config to use the wireless backup. Doesn’t appear to be an option though so likely will try PoE injector unless a Sonos rep has different suggestions. ‍

Well, glad you’re half the way there. These are such new devices, it may require some extra research for a rep to read up or ask questions on. 

Update on this - the PoE injectors worked. Using a PoE switch will not allow the Era Pro 100s to enter wireless mode and sync as surrounds. I used Ubiquiti PoE injectors.