Gitlab creates one pipeline per commit/tag in git. But for this, the commit needs to have a gitlab-ci file defined.

If your old commit does not have the file, is not possible to run a pipeline directly.

One posible solution could be to create a new branch starting from the old commit you want to run in a pipeline, and add one commit in this branch with the gitlab-ci file. This should create a pipeline with the code in your old commit.