@TP-Link so it wasn't a problem with the deco, it was with the modem. I only changed the Ethernet port from 1 to 2 in the modem and that's it. Problem solved. Thx

So It didnt work. Downgrade still down. If I connect my pc directly to the router it work ok. Strange thing that upload its ok. I already try as access point and still the same issue. Any advice?

Since last update my download speed reduced a lot. I have 125 mbts and now with the Deco M9 Plus(US)_V2_1.5.5_210519 update it goes down to 2. Will try downgrading my deco . updating soon