It may take a few minutes for the network to start-up again so give it 2-5 minutes to make sure everything was able to boot up as it’s supposed to and then check your Samsung Galaxy S9 to see if the internet is working or not. If not, then you might want to check out some more troubleshooting tips below.I am sure that you will be able to resolve the connection issues with one of them.
Authentication issues are often (not always) a problem with the password.
It tries to verify/authenticate the password that you are using to log into your router/network and if the password is wrong then it fails to authenticate and will show an Authentication failed error message.
If rebooting your network didn’t help, then try rebooting your Samsung Galaxy S9.
Simply select the restart option or choose to turn it off entirely and then boot it up normally. If not continue to the next page for a possible, fix.
Following the first step in this article and triple checking the password can usually help to resolve authentication failed errors and allow you to get back on track and connected to your network once again.