管理画面は出るが、正しいID、PWでもログインができない。

はじめて投稿します。ご教示よろしくお願いいたします。
現在、管理画面は正常に表示されるのですが、以下の事象が出てしまいます。

正しい）ID/PWでログイン試行、エラー出ず、ID/PWが消えログイン画面に戻る。
誤った）ID/PWでログイン試行、ID/PW違いますというエラー表示がログイン画面に表示。

また、PW再発行を試行すると指定先へメールは送られてくるが、リンクが毎回切れており、再発行ができません。

更に、Jetpackログインも『エラー: このサイトの Jetpack 連携に現在問題が発生しています。』と返されてしまいます。

▼直前の操作
・直前にログインしていた時に、管理画面設定内で、アカウントパスワードを変更をして、（いつもJetpackでログインしていたので、忘れたため変更しました。）

▼現在、こちらで試行したことは、
・サーバー内の復元
・プラグイン、テーマの無効化及び、ブラウザのキャッシュ、cookiesの削除を行いました。
・本フォーラム内の投稿を読み、エラー表示を行いました。
下記の様に沢山のエラーが返ってきたのですが、プラグイン系は削除等試したのですが、どこがよくないのでしょうか。
手詰まりの状態になっておりどなたかお助け頂けないでしょうか。
よろしくお願いいたします。

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