Which Roku Express? The model number is always helpful. Settings > System > About
Older models support 2.4 GHz band only, and Comcast/Xfinity is notorious for changing the settings on that band from b/g/n to g/n, which will affect connectivity.
Let us know which model you have, and the 2.4 GHz settings (b/g/n, or g/n, or something else).
Roku Community Streaming Expert
Note: I am not a Roku employee.
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