Slow wifi on newly installed xer10 with a new fiber run.

I had a tech out to install Xfinity fiber and the new gateway a few days ago. When he left, the Wi‑Fi speeds looked great—around 800 Mbps on our 1 Gbps plan. Since then, I’ve been checking the speeds regularly, and they’ve dropped all over the place. We’re seeing anywhere from 50 Mbps to 300 Mbps on Wi‑Fi, and sometimes the signal even drops completely.

When I plug directly into the XER10, the wired speeds are perfect—right at 1 Gbps—so the issue is definitely the wireless side. It’s not our devices either. We still have our old provider active while we test Xfinity, and those same devices get around 700 Mbps on that network with no drops. So the problem is clearly with the Xfinity gateway.

I’ve restarted and reset the router several times. One restart helped briefly, but the speeds went right back to being slow and inconsistent. I also renamed the 5 GHz band to make sure my devices were connecting to the right one, but that didn’t fix anything either.

Another issue: I can’t get into the gateway settings at all. The usual admin/password login doesn’t work, and I’m hesitant to do a full factory reset and lose everything unless that’s truly the next step.

At this point, I’m trying to evaluate Xfinity against the provider we already have, and honestly… Xfinity is losing. The wired speeds are great, but the Wi‑Fi performance has been disappointing.

Any help or suggestions would be really appreciated. Thank you in advance!