Import from an exsiting gitlab with url failed

Hi, i had an old version gitlab instance 10.3.5, and a new version gitlab instance 12.1.3. When i import project from old to new by using url, it always failed, and the application.log shows message like August 08, 2019 13:57: The Lfs import process failed. 5:GetRepoPath: not a git repository '/data/gitlab/git-data/repositories/base/service.git' . When i check the repositories folder, i found that there is only service.wiki.git, the service.git is missing.
Thanks for any help!

Hello,

I currently experiencing the exact same issue.
Is there a way to get it work’s ?
Someone has an answer, a link ?

The export format changed between those versions of GitLab. Exports from 10.3.5 are not compatible with 12.1.3.

https://docs.gitlab.com/ee/user/project/settings/import_export.html
has some documentation on when the export format changed, but in general you should not assume that you can import projects that were exported using a different version.