Logcat not showing errors from my Huawei P9 phone

Huawei disables LogCat and any access to the logs of your phone. You should go to a hidden menu where you can enable these functions.

1. Open your Dialer app and enter the following code: *#*#2846579#*#*.
2. Enter the Background Settings page.
3. Click on “Log Settings”
4. Check all 3 options to enable full logging.
5. Ignore the "will affect performance" warning.
6. Reboot the phone.

This helped me, hope it will help to you, too.

Source: https://www.xda-developers.com/huawei-phones-disable-logcat-heres-how-to-restore-access/