Elasticsearch's status became red. but I don't know what is wrong with it.Can someone help me? Thank you!

Hello,My elasticsearch's status became red.and I use the plugin named kopf
to look up the status.
I show me like Pic:2.png
You will see one of shards wrong. Its color should be green like the others.

It has more error details in Pic:1.png

Can someone help me and tell me What may I have a wrong setting!
Thankyou so much!

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