Should work.  Might be a setting on the TV.

Iv tried that. It still wont work. Doesnt give me an option to switch the audio output  

CEC must be turned on in order to use an ARC/eARC connected device.  CEC is named differently by different manufacturers:

• OC: E-link
• Hitachi: HDMI-CEC 
• LG: SimpLink
• Mitsubishi: NetCommand for HDMI
• Onkyo: RIHD (Remote Interactive over HDMI)
• Panasonic: HDAVI Control, EZ-Sync, or VIERA Link
• Philips: EasyLink
• Pioneer: Kuro Link
• Runco International: RuncoLink
• Samsung: Anynet+
• Sharp: Aquos Link
• Sony: BRAVIA Sync
• TCL: Control other devices (CEC)
• Toshiba: CE-Link or Regza Link
• Vizio: CEC

 Hey TV guys.  How about we all agree the setting is CEC!!

Okay so just tried this, anynet+ was already on. Sonos app doesn’t detect that I’m connected to ARC (tv doesn’t have ARC, only eARC) even though I am…

Okay so just tried this, anynet+ was already on. Sonos app doesn’t detect that I’m connected to ARC (tv doesn’t have ARC, only eARC) even though I am…

Double check that the HDMI cable from the Beam is connected to the eARC HDMI port on the TV.  If that isn’t the problem, unplug the TV and Beam from the wall.  Wait a couple minutes.  Plug in the TV and then the Beam.  This will force an HDMI handshake. 

As you mentioned Anynet+, I understand you have a Samsung TV. Check this article: https://www.samsung.com/latin_en/support/tv-audio-video/how-to-use-hdmi-arc-on-samsung-smart-tv/ and try these steps:

Depending on the series, make the following settings on your Smart TV so that the sound is then reproduced by your speaker:

• Smart TV from 2017 (T / Q, R / Q, N / Q and M / Q series)
  Open Home> Settings> Sound> Sound Output. Select Receiver (HDMI) from the list.
   
• Smart TV from 2016 (K series)
  Open Home> Settings> Sound> Speaker Settings. Select Receiver (HDMI) from the list. 
   
• Smart TV from 2015 (J series)
  Open Menu> Sound> Speaker List. Select Receiver (HDMI) from the list.
   
• Smart TV from 2013 to 2014 (F / H series)
  Open Menu> Sound> Speaker Settings. Set the TV sound output to the receiver.
   
• Smart TV from 2011 to 2012 (D / E series)
  Open Menu> System> Anynet + (HDMI-CEC). Set the Receiver function to On

If the above doesn't work, try this:

Diagnose your HDMI connection

When your TV has no sound, or intermittent sound drop, and you are listening to something from a device connected with an HDMI cable, one of the simplest potential causes of the issue is that the cable is low quality. Since replacing the cable with a higher quality cable is not always easy or convenient, Samsung Smart TV models have a setting that can be used to adjust how the TV interprets the HDMI signal and improve compatibility with the cable.

Navigate to Menu > Support > Self Diagnosis > Signal Information > Signal History > HDMI Delay Level, and select from one of the options:
(From 2020 model: Menu > Support > Device Care > Self Diagnosis > Signal Information > Signal History > HDMI Delay Level)

• Basic: This is the default setting for normal operation.
• Slow 1: This adds a slight delay before determining that the HDMI cable is not sending a signal.
• Slow 2: This adds a significant delay.

Setting this option to Slow 1 or Slow 2 will improve the signal quality from a poor HDMI cable, but a side effect is that this delay will also occur when changing the source.