huawei 3g usb modem internet doesnt connect

i just installed netrunner rolling . it detects my 3g data usb huawei EC1261 modem but when i try to connect it. it fails. it doesnt connect to internet. it says connection fails.

why it only happens on arch based linux ??

other ubuntu debian based edition (netrunner 16) it connects very fine. but why on arch manjaro it doesnt connect ??

Need help.

It should work with networkmanager as long as the device is in modem mode. There could be a package or setting missing that ubuntu makes that Arch does not?

now how to check log files to see whats happening. it detects my EC1261 HUAWEI DEVICE when i create new connection in netwrok settings. but when i connect its not connecting.

i am new to arch. can u tell me the command.??

I’m not sure since I don’t use 3g modems but these may be of some help:
https://wiki.archlinux.org/index.php/USB_3G_Modem
https://wiki.archlinux.org/index.php/3G_and_GPRS_modems_with_pppd

https://wiki.archlinux.org/index.php/Huawei_E173s
https://wiki.archlinux.org/index.php/Huawei_E220
https://wiki.archlinux.org/index.php/Huawei_E1550_3G_modem

the links i can find but before that how to check system log files and error report. i want to understand why its not connecting.
whats the command to take detailed logcat.??

edited : ok i found how to take logcat. i will check.