Often, when a user attempts to login to ArcGIS manager through online, although the username and password is correct, it will display,
The username or password you entered is incorrect.
however clicking Login a second time allows user to login without issue.
What could this be a symptom of?
I have seen a similar question that suggests that one should preface a domain, however I am fairly sure that the ArcGIS Server is configured using a standalone server (therefore I'm unsure what domain to preface the username with).