It’s not normal. Here are what the status LED’s represent: https://support.sonos.com/en-us/article/sonos-led-lights

It sounds like the Arc is getting/(trying to get) an IP address. I would check your routers DHCP server and maybe reserve its IP address in the reservation table. Ensure you have not disabled the Arc’s WiFi adapter as the 5Ghz radio is required to communicate with the Sub & any surrounds.

If not in use already, perhaps set the router to use a non-overlapping WiFi channel, either ch1, 6 or 11 also try rebooting the router and all your Sonos players. 

I’m just assuming here that you have not wired the Surrounds or Sub, but it’s not clear if you are using SonosNet?

Thanks for replying Ken.

So I have actually already tried to reserve the IP address to the Arc in the router. I have also tried changing WiFi channel from auto to 6 without any success. I have also rebooted everything including the router. Also done factor reset of the TV, Arc and Sub.

Wifi is enabled for the Arc and Sub in the Sonos app and if I look under the network tab in the app I can see SonosNet-channel 1 which is greyed out. And under manage networks I can just see my WiFi which the Arc should be connected to I think :)

When I first connected the Sub I did it in the Sonos app without any problems. And no I don´t have any surrounds yet, just an Arc and Sub Mini.

Nothing is wired at the moment but I have tried to wire router --> Arc but still the same problem.

It´s so weird that it´s just flashing when the audio source is PCM. And as I wrote before, the Sub is working with PCM sound but the Arc is flashing the white led.

@ozzon,
Do you have anything ‘wireless’ quite close to the Arc, or Sub, that might cause either of them any interference - A router, WiFi access point, or maybe a baby monitor etc?

Have you tried a different HDMI cable between the TV and Arc? Also, is the TV firmware and Sonos software running on their latest versions? 

If the issue persists after considering these things, then it maybe best to go onto submit a Sonos system diagnostic and either note/post it’s reference back here and then contact/chat with Sonos Support Staff via this LINK  and see what the Staff can suggest to resolve the matter.

If you do discover the answer to this one, then please report back, as I’ve not heard of this before and would really be interested to know what is causing this issue. (Thanks).

Thanks again for replying!

Everything is updated to the latest firmware and I don´t have any wireless stuff in the TV rum except from the Arc, Sub and cell phones. I always turn off the internet connection to the tv, just enable it when new updates comes out. My Xbox and Shield are wired.

Thanks for the links. Yes, I probably have to contact the support. I will wait until tomorrow and see if someone else have heard about this issue. Of course, I will post if I find any solutions :)

Just a quick update.

After talking to Sonos support and some troubleshooting they sent me a new Arc that I received yesterday. Now everyhing works and no flashing when playing PCM audio.

Ah thanks @ozzon for poppin’ back and reporting the outcome. Glad to hear you got it sorted.