How to connect WP76xx to the Internet by AT command without Legato


We are trying Internet connection by AT command for simple test of WP76xx.
But that does not work.

Currently, Windows PC is connected with MangOH Green with a USB cable. MangOH Green accepted AT command after power on. And the APN has been set. After this, ATD*99***1# was sent to the modem port, and PPP was started. However, NO CONARRIER was returned immediately after CONNECT. CEER result: + CEER: EMM attach failed

The SIM used in the test can be connected with MC7430.

Could you tell me the settings and procedures to connect the WP76xx to the Internet without Legato?