Diagnosis
The Leisure 3W's built-in WiFi is a bit finicky and has a limited range. The most common culprit is your router broadcasting on the 5GHz band, which this projector doesn't support. It can only see 2.4GHz networks.
How to Fix It
First, confirm your network. 1) On your phone or computer, check if your WiFi network name has "5G" or "5GHz" in it. If it does, you need to connect to the 2.4GHz version of your network. 2) On the projector, go to Settings > Network. 3) Manually scan for networks. Look for your network's base name (without the 5G label). If you only see one network name, your router might be combining bands; you may need to temporarily split them in your router's settings.
If That Didn't Work
Move the projector closer to your router, within 10-15 feet if possible, and try again. Walls and interference can easily break the weak signal.
Heads Up
Even when connected, the built-in WiFi is best for streaming from a phone via screen mirroring. For reliable HD video streaming from apps on the projector itself, a wired Ethernet connection using a USB-to-Ethernet adapter is way more stable.