what error do you get? 

Are you using wpa2? 

Any special characters/spaces used in the ssid/password? It shouldn’t cause issues but I’ve seen a few devices that do have issues

Thanks for responding.

Error message is “incorrect password”.

Yes, using wpa2.

Tablet did connect. Phone did not.

Six other devices are connected.

Password is consists of only capital letters and numbers.

Any suggestions would be appreciated.

Any spaces? 

If you change the ssid/password, does the tablet/phone connect?

No spaces.

Have not tried changing password. Don’t want to have to login the already connected devices

Since you are not able to connect with Wi-Fi on your Samsung phone and tablet with default Wi-Fi password, I suggest you to factory reset the modem and try to connect it again.

Let me share you the link to perform a factory reset for your reference:

http://arris.force.com/consumers/articles/General_FAQs/SVG2482AC-Factory-Reset

I’d start with trying different ssids and if that doesn’t help, then try the factory reset. 

Hope you were able to connect to your Samsung phone after trying on the Reset.

Were you able to succeed in connecting to the Samsung phone by changing the Wi-Fi name and pasword?