hi, is it possible to scan imsi of mobile phones around?

First of all, thank you, you have a question:
i check my imsi, switch mobile to gsm mode, check cellid, then select grgsm_livemon correct frequency.
But with the command “sudo python3 simple_IMSI-catcher.py -s” it can’t find my IMSI, even though it shows a lot of IMSIs in the list.
Then, use it again with the command “sudo python3 simple_IMSI-catcher.py -s -m xxx”, where xxx is the IMSI just found with the -s option, but this command also has no results.
You ask yourself why the search command by IMSI does not have such a response.
Thank you again and look forward to your feedback.
Thank you.