Diagnosis
A resolution/refresh rate handshake failure between the Switch and the projector's HDMI port. The Capsule 3 Laser requires a specific signal format.
How to Fix It
Power cycle the entire chain. Turn the Nintendo Switch off completely. Unplug the HDMI cable from both devices. Power on the Nebula Capsule 3 first and let it boot to its home screen. Then reconnect the HDMI cable to both devices. Finally, power on the Switch.
If That Didn't Work
Manually set the Switch's output resolution. On the Switch Home menu, go to System Settings > TV Settings > TV Resolution and select 1080p. Ensure RGB Range is set to Automatic.
Heads Up
The projector's HDMI port is version 2.0. It will not pass through HDR signals from the Switch. If HDR is enabled on the Switch, it can cause a 'no signal' error. Disable HDR in the Switch's TV Settings.