nicklamb on "[Plugin: WP Broadbean] trying to post but getting a fail response"

I keep getting a fail response when trying to post from Broadbean network portal. Also when I visit my testing URL/?wpbb=broadbean I get the error message "Sorry username and/or password are not valid."
I've checked and the Username/password combo in the XML feed matches the one set in wordpress admin - can you think of anything else that would cause this?

https://wordpress.org/plugins/wpbroadbean/