Your post are a little confusing but I think I now understand your situation.
Your client made a Roth contribution but income level was to high, so it was recharacterized to a nondeductible traditional IRA.
Let's say for example the contribution was $6,000.
Your client can now do a back door Roth by moving the $6,000 to a roth by a rollover or trustee to trustee transfer. That would be an irrevocable conversion once completed.
If your client has made tax free traditional contributions he is subject to tax on the conversion due to the pro-rata rule.