What's the matter with girls suddenly not texting me?

The reason remains to be understood. Don't affect your mood too much, and handle it properly after finding out the situation. Confusion and incomprehension are unpleasant. Get to know it in a proper way! Be prepared for two kinds of psychology, even if the other party doesn't want to keep the previous relationship, don't be too unhappy. I wish you peace of mind and welcome a new day!