Failing to register from Asterisk - wrong password

I get the following when Asterisk registers:
Jun 10 16:19:04 WARNING[11968]: chan_sip.c:9740 handle_response_register: Forbidden - wrong password on authentication for REGISTER for 'nikberry' to 'voipuser.org'

I've reset the site password, and from the sip account settings reset the sip password to be the same, but it still doesn't work.

Hi Nikberry,
Your sip password is the original password you took out for the site- It does not get reset by changing the password.

Recheck you have the correct registration string and hold fire for a day or two- There are some server issues at this end

OK. I'll wait

Two points, though. There are two versions of the registration string given on this site. One suggests
register => nikberry:<password>@voipuser.org/4484493343472

the other
register => nikberry:<password>@voipuser.org/084493343472

I've tried both.

Secondly, the 'My SIP Account' page gives an option to reset your SIP account password to your current voipuser account password. That's what I used.

Nik

The registration string uses the international dialing code version of your number i.e. 44844....