Here is an article that addresses your question Google Removes Your Manual Penalty But Your Rankings Won't Improve:
In early September, I talked about this in a poll I ran asking Does A Manual Action Removal Impact Google Rankings? We have almost two-hundred responses and the sad results are in.
53% said their rankings never improved, even after a year. 12% said they saw a ranking improvement within days, 14% said within a month, 8% said within 3 months, 7% within 6 months and 7% within a year. But 53% said never.
Here is another article that explains why rankings may be slow to return or may not return at all:
Many people are surprised when a penalty is removed and they don't see any movement in ranking. Google may employ more than 200 different signals when determining SERPs, but links still carry the most weight.
Remember all of those "unnatural" links that you just removed and disavowed? In addition to being unnatural, many were still quite powerful and responsible for your pre-penalty ranking success.
Google's John Mueller says that your website may need to "regain trust" after a manual penalty because algorithms may have picked up on the same problems for which you received the manual penalty:
...it looks like our algorithms have picked up on that too. So while resolving the manual action is a good way to start, you need to keep in mind that it can possibly take quite some time for our algorithms to regain trust in your site even after that.