"I created the work item and it isn't on the board." The cause is almost always one of two things.
1. Its status isn't in a column. A board column is a bucket of one or more statuses. If a status is in Hidden statuses (called Unmapped statuses on classic boards), every work item in that status is hidden from the board. Adding a status to a workflow does not automatically put it in a column on every board.
Fix: on the board, open ••• → Configure columns, drag the status from Hidden statuses into a column and Publish. On a classic board this is under Board settings → Columns.
2. The board's filter excludes it. The board shows whatever its saved filter returns. If the filter limits by space, work type, component or label, items outside it never appear. Check Board settings → Details → Board filter.
Rules that cause the rest of the confusion
- A status can sit in only one column per board, but a column can hold several statuses.
- Jira treats the right-most column as done. Put
Won't Do and Cancelled there as well, or the work items carry over when the sprint closes. - Board colours come from the status category (To Do / In Progress / Done), not from the status itself. A status in the wrong category quietly breaks velocity and burndown.
- Can't drag a card into a column? That means there's no workflow transition from the card's current status to the statuses in that column. It isn't a board setting.
Default statuses, adding and renaming statuses, and the JQL that finds work by status history (status WAS, status CHANGED FROM … TO …) are covered here: Jira status guide
Disclosure: I'm with Redmoon Software, a Marketplace vendor. The guide above is free and has no sign-up.