Any chance that they have been auto-archived to cloud storage?
My S7 wont let me see the pictures in the gallery on my pc, but only the ones i took after the 31/3, i can see them on the phone but when you go S7>Camera>DCIM etc it only shows upto the 31st.
Any chance that they have been auto-archived to cloud storage?
Do you have an sd card in the phone?
If so, they they maybe stored on there.
Check the settings on the camera to see if it saving to memory card rather than phone memory.
Or open a photo (on your phone) that you can't see on pc & swipe up on the picture - you will then see the details & will show where it is stored.