That message is confusing because it prints two options back-to-back.

It is not one command.

Try this:

In the same folder Railway is building from, run only:

pnpm install --no-frozen-lockfile

Commit the updated lockfile.

Redeploy with install command set to:

pnpm install --frozen-lockfile --prefer-offline

If it still fails, it usually means Railway is building from the wrong root directory (or there are multiple lockfiles in a monorepo). In that case, check the service Root Directory and make sure the lockfile is in that exact folder.