Problem 

The create button only returns a warn message with the following text: "Cant Can't create the issue. The configured Jira responded the following..." 

Solution

One or more required Fields fields are not included in the "Issue Form - create form" or hidden (and there is no default value specified).

You can:

• Include the Fieldfield.
• Specify a default value or unhide the field.
  

Problem

The create button only returns a warn message with the following text: "Anonymous access must use CAPTCHA."

Solution

Since version 2.3,  non logged in users of Confluence, who are not logged in to Jira, can create Jira Issues. But these users have to fill in a captcha.

...

• Disable anonymous access to the page.
• Add the "Issue Forms - captcha "-Macro  Macro to the form.