When I turn on the DDJ-ERGO’s power after launching TRAKTOR 2, I cannot select the DDJ-ASIO driver.

Have you launched TRAKTOR 2 after turning on the DDJ-ERGO’s power?

If the DDJ-ERGO’s power is turned on after launching TRAKTOR 2, the DDJ-ASIO driver may not be recognized.

If the DDJ-ASIO driver is not recognized, quit TRAKTOR 2, then restart the DDJ-ERGO.