The page object that can be used to configure the JenkinsDatabaseSecurityRealm in acceptance tests has a typo in the element name used to enable/disable the ability for users to self-register (ie. signup) when using this realm. The jelly form control is named "allowsSignup" but the pageobject references it using the name "allowSignup". This causes any ATH tests that rely on manipulating that element to fail with an element not found/Timeout exception.
This was brought to light as the result of a recent change that forces the UI behavior to disable user signup by default (as a security precaution)., which in turn caused some tests, which expected this to be enabled by default, to break.