Make sure that your `udev` rules are configured [correctly](https://doc.satoshilabs.com/trezor-user/settingupchromeonlinux.html#manual-configuration-of-udev-rules).
Then, install the latest [trezor_agent](https://pypi.python.org/pypi/trezor_agent) package:
Make sure that your `udev` rules are configured [correctly](https://support.keepkey.com/support/solutions/articles/6000037796-keepkey-wallet-is-not-being-recognized-by-linux).
Then, install the latest [keepkey_agent](https://pypi.python.org/pypi/keepkey_agent) package:
Make sure that your `udev` rules are configured [correctly](http://support.ledgerwallet.com/knowledge_base/topics/ledger-wallet-is-not-recognized-on-linux).
Then, install the latest [ledger_agent](https://pypi.python.org/pypi/ledger_agent) package:
If you can't find command-line utilities and are on macOS/OSX check `~/Library/Python/2.7/bin` and add to `PATH` if necessary (see a [relevant](https://github.com/romanz/trezor-agent/issues/155) issue).