Hello
If your Roku 3 player is not connecting to WiFi, it is possible that the WiFi signal from the router is out of range. In order to strengthen the signal, move the router and Roku 3 so that there are fewer objects and walls between them.
For any help or support just visit us: www Roku Com Link
When you say WD box, do you mean a Western Digital Hard Disk Drive? If so, get a Solid State Drive (SSD), and connect it via USB3.
The HDD or the USB connection is not fast enough to keep up with the required speed of the video.
If you mean something else, please add details.
Check the high voltage circuit on the board that has the 120 volts input. The high voltage should be close to 400 volts - nothing less than 390 volts. The capacitor is failing to hold the voltage and needs to be replaced.