> After activating the context, run test/list-contexts in oFono git.  What
> does it say?

/usr/lib/ofono/test/list-contexts
[ /sierra_1 ]
    [ /sierra_1/context1 ]
        Username =
        Protocol = ip
        Name = Internet
        Settings = { Interface=wwan0 Method=dhcp }
        IPv6.Settings = { }
        Active = 1
        AccessPointName = objcPpublic
        Password =
        Type = internet

for me it's ok. i have made a test to add a "address" to 0.0.0.0 and 
get this.

/usr/lib/ofono/test/list-contexts
[ /sierra_1 ]
    [ /sierra_1/context1 ]
        Username =
        Protocol = ip
        Name = Internet
        Settings = { Interface=wwan0 Method=dhcp Address=0.0.0.0 }
        IPv6.Settings = { }
        Active = 1
        AccessPointName = objcPpublic
        Password =
        Type = internet

but in either cases i got connman getting an address..