New phone - authentication error on wifi connection

[JStone]

Around 5 years ago I helped Friend set up a wireless modem / router at home. All worked fine - a variety of Android, Mac & Windows windows devices (phones, tablets, laptops etc) have successfully connected.

Until last week, when Friend bought a new phone. All the other devices can still connect, but every attempt to connect the new phone results in "authentication error occurred" message on the phone & no connection. I'm baffled, and frustrated because it's bound to be something trivial.

ADSL Modem / Router - Netgear DG834G - other devices can still connect, but not the new phone. Firmware up-to-date, & log files ok, so don't think it's a fault with the router.
Old phone - Samsung Galaxy S3 mini - still connects to Friends wifi & elsewhere.
New phone - Samsung Galaxy J3 - connects ok to other wifi networks (mine, local cafe & library, shop where purchased), & to mobile network, so don't think it's a fault with the phone.

Have rebooted router & restarted phone.
Password is correct. Using WPA2-PSK. Have tried forgetting the network then reconnecting, and also tried using incorrect password followed by correct password.
Access control is *not* active (ie not blocking unlisted MAC addresses). Tried applying access control with new phone MAC address added - no joy.
Tried clearing Android system cache - no good
I'm not familiar with Android phones, so not sure what to try next.

I could suggest Friend request refund / replacement phone, but without understanding the cause could end up with the same problem.

Any suggestions?

[Afasoas]

How old is the current firmware on the wireless access point?

I had the opposite problem where by new firmware for my access points didn't play with older unpatched Androids late last year. If the netgear firmware pre-dates October 2017 and the device connects with more recently patched wireless access points, I suspect this might be the issue. If not, then I'd start to look harder at the phone.

[JStone]

How old is the current firmware on the wireless access point?

I had the opposite problem where by new firmware for my access points didn't play with older unpatched Androids late last year. If the netgear firmware pre-dates October 2017 and the device connects with more recently patched wireless access points, I suspect this might be the issue. If not, then I'd start to look harder at the phone.

Firmware was several years old (though it's the latest release).

I gave up trying to understand what was causing the problem, and simply replaced the router with a slightly less old one that had been sitting in a cupboard gathering dust since I upgraded our own network - so far, so good.