My Roku Express (3930, 3931 series) (Model: 3930X) was purchased at a retailer. After plugging it in and setting it up, a software update began and then the device stopped working. I fear that this model device is no longer supported by ROKU. I am trying to do a warranty exchange for a supported product, however you need a serial number to complete this process. After entering my serial number found on the device (SOOO831A46W7J) the website says it does not recognize a valid serial number. This loop makes it impossible to exchange this product. I went to the retailer and they were unable to help either. Their system said to contact ROKU.
If you want to try and complete the installation again, you can Factory Reset your Roku device by pressing and holding Reset button/pinhole for 30+ seconds and then connecting to either a mobile hotspot on the 2.4ghz band or verifying that your network is configured to use the b/g/n wireless mode/protocol (rather than merely g/n) and try your setup again.
Also, make sure you are using the power adapter plugged into a wall outlet during setup rather than the TV's USB power port if you are currently doing that.
Normally, the mobile hotspot is recommended to get through troublesome setups.
If you have a cable ISP (Xfinity, Cox, AT&T), you will need to verify that your wireless mode is set to b/g/n to avoid a known connection issue with these ISP routers.
You mentioned that the device stopped working. Could you tell us more about it? Did you see an error code or message? Please let us know as well how are you powering your Roku device. Is it connected to the USB port of the TV or to a wall outlet?