It could possibly come down to your NAT on the 360 not communicating with your current Internet connection, i want to say Modem but as you have said there isn't one. Just to double check, the cable you connect to that doesn't require a modem are there multiple connections connected that are working successfully apart from the xbox one.

How to Fix Common Xbox 360 Wireless Networking Problems May 08, 2020 How to Fix Xbox Live Error 8015190E? - Appuals.com Nov 15, 2019

You can connect your xbox 360 to xbox live via a modified router in order to wirelessly connect to xbox live: How to connect wirelessly to xbox live using a modified router Hope this helps you connect wirelessly to xbox live with a laptop!:) If you still need help, I have just finished a new E-Book (see below) with even clearer instructions

How to Fix Common Xbox 360 Wireless Networking Problems May 08, 2020 How to Fix Xbox Live Error 8015190E? - Appuals.com Nov 15, 2019

Mar 27, 2020

Xbox Live Benefits on Xbox One. Keep in mind that your previously purchased Xbox Live subscription plan will work on the Xbox One. Let's say you have 5 months of Xbox Live on your Xbox 360 How to play online with a RGH/JTAGGED Xbox 360 - Quora The best answer for your question is coming from one of the top RGH/JTAG Console sellers in the US (www.shadowmodz.us) An RGH/JTAG Xbox 360 CAN go online with one thing: A stealth server Stealth servers are paid servers that an RGH can connect to