Which module/communication protocol are you using: Bluetooth classic (HC-05, HC-06) or BLE (HM-10) ?

In case of HM-10, have a look at
https://blog.yavilevich.com/2018/04/sho … 8-is-here/

Oh... many thanks guy, looks like i see light at the end of tunnel. I'll report the progress.

Check the location permission if you want to use BLE on recent Android phones

I've tried that, still no luck.

welcome
I go on this link
http://remotexy.com/en/help/start/arduino-hc05/

You must carry the application in the phone؟

I go on this link
http://remotexy.com/en/download/

........   

Thank you for your nice response, but it's not about the HC-05 or 06. It about blue tooth's driver in phone. I found that newer model phones could not connect to the board, while older one worked well with the same board. I dig into phone spec. and found that old phone use blue tooth driver v.4 while newer phones use v5.

You must carry the application in the phone؟

I go on this link
http://remotexy.com/en/download/

........