Warband Bank Error

[Tyrskorn]

Sounds like you found it already, but Warband banks are indeed temporarily disabled. More info and future updates here:

Warband Warbanks are Temporarily Disabled

Along with the launch of the pre-expansion patch (11.0.0), we’ve temporarily disabled the Warband Warbank while we work on a critical issue. This is a top priority and we intend to enable the Warbank as soon as possible. Thank you!