This error occurs because of a missing custom pull secret in the dynakube.
In older versions of the operator, this error was ignored, and reconciliation continued since we trusted the node to be set up correctly so the image would be pullable. This is not the desired behavior since the Operator does not know which version is actually rolled out and can therefore not prevent downgrade and provide other benefits. Since v0.11.0 the operator supports token-based authentication, whereas before, it was only possible to use username/password-based authentication.
Moreover, with v0.12.x+, the Operator check is improved and must have the same custom pull secret as is configured on the node.
To solve the problem, add a custom pull secret to Dynakube and reapply the dynakube.