I have seen this issue many times in multiple Lianas, even at 3s. I have saved a few Liana owners the haaale with this.
The switch goes dead due to 3 reasons.
1- error code in kit. Can be resolved by switching car off and then on.
2- blown cng kit switch or broken wire of kit which is the most common.
3- blown switch which is unlikely in an FF cng kit unless you give it very high voltage in reverse polarity or burn it or break it. In mist cases, the kit will shut down to save itself.
Sent using Curiosity's onboard communications sytem.