@David-TP yes, the issue started recently.
 

Correct- when I use my smart phone with Alexa app and I issue drop in command, it does work with all echo devices. However, when I try to drop in from any of Echo devices, it doesn't work (it seems it try toestablish collection for a one-two seconds and then drops. )

  @David-TP Thanks - there are 6 Alexa echo devices ranging from echo show 15 and 8, three echo spots and one older echo dot. They are connected to main network which is Deco mesh (2.4 GHz +  5 GHz). They operate normally with other services like music streaming, podcast, watching YouTube etc. it's just this drop in feature which doesn't work. I read somewhere that Deco is potentially flagging it as malicious and thus blocking it.

I presume new firmware needs to be done manually for each Deco device (I have three of them)?

If installing new firmware doesn't solve the issue, what else can be tried? Is it easy to go roll back to previous firmware if new one cause potential issues ?

thanks again.