Unable to create (first) Workbench application ("Failed to create application, please check if application name contains invalid string).

Connection to local Livecycle server (ES4 trial) is working, service provider configured normally - Repository service 1.0 provider service is "RepositoryProviderService".

Error message is ambiguous and issue is definitely not with application name. This is a fresh installation so this may be a common pitfall with installation or configuration.