Diagnosis
Weak or unstable Wi-Fi signal to the mounted location. The Show 15 has a less powerful antenna than a router.
How to Fix It
Check signal strength. On the screen, swipe down from the top. Go to Settings > Device Options > Network. Note the signal bars. If low, your mounting location is the problem. Consider a Wi-Fi extender or repositioning your router.
If That Didn't Work
Interference from the power cable or metal in the wall. Try a different Wi-Fi band. Force it to connect to your 2.4GHz network in the Network settings. It is more stable over distance than 5GHz.
Heads Up
Do not perform a factory reset as a first step for Wi-Fi issues. It is almost never a device software problem. It is an environmental network problem.