관리페이지에서 에러 발생하면 파일을 로컬에 받고 직접 업로드하는 것이 보통입니다. 상관있는지 없는지 모르겠으나 호스팅 여유 용량도 체크하는 것도 기본 사항이고요.
아래 링크 내용도 참고해보세요.
https://wordpress.org/support/topic/getting-download-failed-error0d0890a1asn1-encoding-routinesfunc137reason#post-7376391
This error is caused by your server having an outdated version of curl and/or the OpenSSL library.
Modern SSL certificates are signed using the SHA-256 algorithm, which your older code lacks support for. You need to update your server, or if you have a webhost, they need to update it for you.
https://wordpress.org/support/topic/getting-download-failed-error0d0890a1asn1-encoding-routinesfunc137reason#post-7387690