Why there are some particular fields not editable?

Summary

Some fields are grayed out, and cannot edit.

Answer 

It could be due to the following reasons:

• Those custom field types may not be supported in this app

• Those fields may not exist in ‘Edit issue screen’ of Jira

If a row (issue) is entirely grayed out, there seems like to be other reasons:

• User don’t have ’Edit issues’ permission for the issue

• Workflow is customized (i.e. jira.issue.editable)