Minoxidil stopped working 7 months ago and I lost all the hair I had regrown. Can you please tell me how to make it work again?

You will find that oral minoxidil works much better. Take a 2.5 mg pill and cut it in two. Take one half a day. See your doctor to ask him for a prescription.  Andrew Messenger from Australia is a strong proponent of this in women. You might also consider oral spironolactone. 

I would recommend the revolutionary  treatment known as PRP, or “Platelet Rich Plasma” It has been shown to be very safe and effective for hair loss for both men and women. It works great as an adjunctive therapy with minoxidil. However if minoxidil is no longer working I would recommend an evaluation by a hair loss expert.

The first thing to understand is that minoxidil does not STOP hereditary hair loss.  Minoxidil is a hair growth stimulant (and a mild one at that - there are better ones available).  What that means is that its use only acts to delay and slow down slightly your inevitable hair loss.
The only way to keep and regrow your hair permanently is to treat the CAUSE of your hair loss rather than just the symptoms.  
Please see a hair loss specialist who has a complete solution that works to both STOP hair loss AND regrow the lost hair.  Any treatment that works only on hair growth will be ineffective.

I agree with Dr Donovan, that a good medical workup will help, and, if all is normal, then maybe try some topical like Nutrafol. Good luck.

Minoxidil may or may not have stopped working. Rather your genetic hair loss likely overcame the ability of minoxidil to halt it. Of course there are other reasons too - including the possibility that you have another diagnosis now as well. Please see your dermatologist or hair physician. Only with a careful and detailed review of your medical information and examination of your scalp can an opinion be given as to what to do next.

When you find that minoxidil becomes ineffective after 7 months, I doubt that you can use it again. Possibly a higher concentration might work