Issues disappear from Khanban board and Time Line

[Dojeon Lim]

Certain issues are not visible and searched on the Kanban board. It was like that all of a sudden about three months ago. And from a month ago, the same phenomenon appeared in the timeline. The status values of certain invisible issues vary. Not only the completed issue but also the ongoing issue has disappeared.

I was solving the issue that could not be searched on the Ganban board as a temporary method by searching the timeline again, but now even the timeline has the same phenomenon, so I can't use that method anymore.

Our Jira type is "Team-managed projects."

[Dave Mathijs]

HI @Dojeon Lim welcome to the Atlassian Community!

Are all statuses mapped to the correct column in the Kanban Board?

Are these issues linked to an Epic?

Make sure that your issues are linked to an Epic in order to display them on the Timeline.

[Dojeon Lim]

All Issues are Already Linked to each topic correctly. 😭

How can I do another method? 

It's also in the right column. Because before, it used to look right in every column. Suddenly, it became invisible, and there were more and more invisible topics regardless of the status value.