Hi. I cut it in the place where the scissors icon appears and when I connect it and turn on that piece that I have cut it does not light up. I do not have activated wifi. Could it be for that reason?
Nope. Make sure that the bit you've cut, and want to light up is the one attached to the plug. I.e you've cut off 50cm you didn't need, as opposed to cutting off 1.5m you didn't need.
Pieces that you cut off Yeelight strip will not light up anymore.
Only that one piece that is attached to wall plug can light up.
Yes.... because that's the bit that has a plug. The strip without a plug is now powerless and won't light up. I'm not sure how you expect it to