Samsung Galaxy A5 2017: Authentication Error and Slow Internet Speed on UPC Wifi

Hello.
The problem is:
I have Tel Samsung Galaxy A5 2017. There was no problem with it until last week, when the phone does not want to connect to the home WIFI network. All other devices can easily connect, there is no limit on the number of connected devices. Previously, I could easily use this wifi on this phone. Usually, when trying to connect to this wifi, the message "authentication error" pops up even though the password is entered correctly. Once the miracle is able to connect, the connection breaks down, and the internet speed on this phone is 8 Mb / s, and on others 300 or 500 Mb / s.
I have already tried to connect via the WPS button, it did nothing.
I also tried to add my device to the MAC list and nothing changed. What's next? Only the service remains?
Internet with UPC, connect box: p

Did you reset the router, did you check if it connects to another wi-fi network? Have you tried hard reset or upload new software? If nothing changes, give it back to the warranty right.

A router reset was done just like the phone's factory settings. The phone connects to any other wifi network, but not the specific home one.

So there is a problem with your wi-fi network. Have you changed the password encryption settings? on what frequency is your wi-fi network transmitting?

I assume that the phone's mac is not on the router's blacklist? From the phone make forget this network and try to connect again.

It looks like invalid DNS.

The phone's Mac is not blacklisted.
I haven't changed the password encryption, where to check the frequency? Forget the network I've already done 100 times
And these DNS's? How to check, change?

In the router settings in the tab should be.

"2.4 GHz and 5 GHz wireless networks are on" is that it?

It's not about something like the movie.
Possibly something is mixed up with the "UDP Protocol". Some operators specifically block this to offload the link.

I do not know if it matters, but there were several devices connected to the router, today I connected two more and there was no problem .. Only in this Samsung I do not want to move ..

When you added a new network to your phone, did you set the encryption correctly?
(WPA-PSK, WPA2-PSK is to be the same as you have set in the router)

Yes, WPA2 PSK is set on both.