Propecia and minoxidil have stopped working. Any reasons?

So both of these medicines are not perfect.  
Propecia/finasteride is only 60% effective.  It has a very short half life meaning it only works part of the day and it only blocks one of the three DHT receptors in the body.
Rogaine only works for about 30% of people, mostly very young men and some women but also is only a mild PGE type agonist (hair growth stimulant).  It is also a vasodilator which means it brings more DHT infused blood to the scalp than would normally be the case.
There are now newer more effective medicines available.  I would recommend seeing a specialist hair growth doctor who can create you a solution based on precision medicine.

You would need to provide alot more information and up close photos of all regions of the scalp to really get to the issue. One can't determine the cause with the limited information provided.

I usually tell patients that propecia and minoxidil take 4 to 6 months to start working. My suggestion would be to continue the medication and give them 1 to 2 years to assess the results,
Dr. Robert Jones