Hello! If you have the SBG8300 let me tell you that this device has the WPS connection and most of the printers have that button too, in this case the SBG8300 does not have a physical button but you can access the web manager page of your 8300, click on this link to check the steps:

http://arris.force.com/consumers/articles/General_FAQs/SBG8300-WPS-Push-Button-Connection

Now, if you printer has a panel of control or screen, most likely in the settings you will see the wireless connection and you just need to enter the credentials as you connect any wireless device.

So, my recommendation is to check the model of your printer and check the manual and then proceed accodingly with the options I gave you.

Most of the time when it is common issue on the old printers. When they try to connected to the wifi, are the security mode on the wi-fi signal is not compatible with the signal of the wi-fi integrated on the printer. So you have to check what it is the best option of this security mode to you printer. Used the guide to located the Security Mode on your SBG8300, and used the manual or faqs of your printer manufacture to located the best Security Mode.

There are going to be several types of modes the most commons used is the wpawpa2-psk (tkip/aes)


https://arris.secure.force.com/consumers/articles/General_FAQs/SBG8300-Changing-the-Wi-Fi-Name-and-Password/?l=en_US&fs=RelatedArticle#:~:text=Under%20the%20Home%20Wi%2DFi,in%20the%20Network%20Password%20field.

Newer devices maybe have problems with this kind of changes.