Does it play when you use the controller, rather than using Alexa?

Factory resets are rarely, if ever, recommended. You should have followed the instructions in the new router - installation instructions FAQ.

What do you mean by controller?

The ‘controller’ is the Sonos app, a remote control, running on your phone, tablet, or computer,  to see what is happening on the Sonos ‘system’ which runs on the Sonos devices. I’m curious (although it may or may not help me) to know if this is a voice control issue, or a Sonos issue. 

The controller is the app you used to set up your speaker on your network. 

I can play from the Sonos app but not the voice control. I ask Alexa and Alexa answers back saying she is going to play but then nothing happens. Any suggestions?

So, your issue is with implementation of voice control, not Sonos playback itself. This is an area I’m absolutely not an expert in, so if someone else chimes in, I’d listen to them. 

I would recommend removing Alexa from your Sonos system, returning it to a ‘pristine’ state. Then I’d reinstall, following the instructions here. 

If it continues to fail, I would 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.

If you factory reset the speaker, it has no voice assistant(s) added.  You need to re-add a voice assistant:

https://support.sonos.com/en-us/topic/voice-services-on-sonos