Mengapa kartu SIM saya tidak bisa Terdeteksi? SIM card not detected

@ginanjarpratama first make sure that it is enabled:

Settings > Mobile Network > SIM card > make sure it is enabled.

If it is then you need to make sure that you have a valid SIM card. Check with your provider and try a different one (a known-good one)

I am sure you already tried to either reboot or restarted you Realme. Press and hold the power button until the power menu appears, then selecting the "Restart" or "Reboot" option.

After that it is possible that this is an issue with your SIM card reader. For that you will have to disassemble your phone and evaluate the reader. Since iFixit does not yet have a guide for this, use something like this video

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!