The error message is likely an indication of a loose connection (wiring) or loss of communication due to some failure with respect to the Asus router: hardware, firmware, or software.
You did mention Asus but the model number is relevant.
Are all devices disconnecting or just your gaming computer?
What you can do is swap out ethernet cables with known working ethernet cables. Especially if one device is losing connection and another device is not.
You can also physically inspect your connections starting at the point where Xfinity service comes into your residence. Just do so safely, no climbing on roofs, poles, etc..
Look for signs of physical damage: corrosion, cables bent, kinked, nails and staples, rodent chews, and so forth.
Inside and outside. Make sure all connections are snug and tight. Pay special attention to any splitters. Small boxes with one cable going in and perhaps 2,3, or 4 cables going out. Splitters tend to fail on a regular basis. Especially outdoors.
[Note: I have Xfinity and routinely beg for an extra splitter or two. When problems occur, the replacement often resolves connectivity problems. Or simply unscrewing the coax connections, blowing out dirt and debris, and reconnecting will fix things for awhile.]
Inside, if you have Ethernet patch panels and wall jacks, there could be a loose wire. May look okay but one wire is not securely in place for the network to function properly.
So when the tech gets there be ready: Have a diagram or sketch of the connections. Clear away anything that may get in the tech's way. Make it easy for the tech to get to things and work/test.
He or she may be limited in what they can do. Maybe just up to your modem or router.
Afterwards, the rest becomes your responsibility.