I don't know what a "Xfinity Seasonal Convenience plan is" so I have no idea if that matters to Roku. (I'm guessing Roku doesn't know what it is either.) 3MB/s is fine if you really mean MB, but internet speeds are usually written in terms of bits/second, not Bytes, so if it's 3Mb, that's kind of low for streaming TV. (Though it can be done - I've done it at 1Mbps but it wasn't nice to look at.) I get lost when you start talking about a house with some Xfinity plan, but then you talk about "another building". Are you hoping the wi-Fi in your home reaches a shed or does the building have something else?
By the way, I believe all of Xfinity's plans say "up to", so it's a good idea to do a speed test, because in some locations, reality can be well short of the "up to".
And I know Xfinity has their hotspots, so maybe you're using one of those?
As for nothing happening, how are you driving it? If you're trying to control it with a phone, that's not going to work until after you get it connected to the local Wi-Fi.
