How long does second FUE treatment start to grow?

It can take 6 to 12 months after surgery to see results.  If you are concerned it is best to contact your doctor

Overall, it's still fairly early and I would not be concerned.  It can take variable times for hair to start regrowth.   Perhaps asking for a PRP injection would help jumpstart the process.  If no growth in another couple months, there is likely an issue.  Follow up with your provider ASAP would be best.   Dr. G

Because of scar tissue from the first procedure, there can be a delay in growth with the second procedure. In most cases we see substantial growth with a second procedure between 6 and 9 months post-op.

No, second FUE grafts do not take longer to grow then first .Regrowing hair is thin, undersized and not bright untill 4-5 th months of hair transplant. İt's normal for new growing hair starting to get native characteristics, waviness, curl in first 4-5 months..This actually takes 10-13 months for hair to become full mature , as thick and bright  as native hair. 

I wouldn't be worried yet, a second transplant may not necessarily grow at the same rate if it's a different sized procedure, in a different area, done by a different doctor, etc. so just treat each one separately. If you don't start seeing new growth starting within the next 2-3 months, that's when you should begin to feel concerned.

The Second FUE transplant will grow at about the same time as the first transplant you had done. No problem having multiple FUE provided that the donor area holds up

usually hair needs to go through its own cycle of growth and grow in after a few months. We have found that after second hair transplant it usually takes longer for hair to start to grow in. If your hair still does not grow after a couple of more months, you need to do a folkow up visit with your doctor.