Unable to index postmeta due to DB error

Hi, I am able to index all tables except postmeta for some reason. I tried some fixes on the forum , but nothing is working.

| wp_postmeta | CREATE TABLE wp_postmeta (

  meta_id bigint(20) unsigned NOT NULL AUTO_INCREMENT,

  post_id bigint(20) unsigned NOT NULL DEFAULT 0,

  meta_key varchar(255) DEFAULT NULL,

  meta_value longtext DEFAULT NULL,

  UNIQUE KEY meta_id (meta_id),

  KEY post_id (post_id),

  KEY meta_key (meta_key(191))

) ENGINE=InnoDB AUTO_INCREMENT=26352759 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci |

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