The PSLF is an opaque minefield run by an incompetent, understaffed loan company, who has no obligation to help its "customers" achieve forgiveness but a strong interest in deliberately tripping up student borrowers every inch of the way to their 120 payments.
I'm theoretically on track for late 2020, early 2021. Like many people I know, I was on the wrong repayment plan for 2 years - the non-income-based 30 year standard repayment plan.
I also ignorantly re-consolidated after my first year, so I lost those 12 payments, even if the plan was correct. I also lost about 5 payments over the years for a variety of reasons: (1) one month hardship deferral; (2) one month on the standard plan because my income re-certification form was late; (3) 3 months of (involuntary) administrative forbearance while Fed Loans was processing my request to switch plans.
Finally, I lost 5 payments on the unsubsidized portion of my consolidated loan because Fed Loan claimed that these payments (made in 2011 to a different servicer) were one cent short of the full payment amount. Mind you, these were direct debit auto-payments taken out of my bank account by the servicer in the amount that they had set. So I had no control over this, and now have no real way to even argue the point.
If I had not re consolidated, had been on the right plan, and hadn't lost those other payments, I would have been eligible this October. Most of people in my shoes have long abandoned this program for the reasons I listed above, and many other similar issue with the loan servicer.
That being said, if you do a reddit search, there are a small number of users who have actually had their loans forgiven already. So it can be done.