At this time of year the days are shorter and cooler and even the torts kept inside seem to sense this and become less active.
Double check the enclosure temperatures, especially at night. Babies need constant warmth day and night; not below 26C and must be able to bask at 35-37C.
Don’t guess. These temperatures indoors vary with the season more than you’d expect. Measure accurately with a digital min/max thermometer to find out the overnight minimum and a temperature gun type thermometer to measure spot temperature directly under the basking lamp.
Make sure that the lights are on full and bright for 14 hours too. You are trying to imitate summer. Use a timer to be sure.