I just did this last month for our vacation Bible school. We did about 40 shirts.
Try this (make sure the iron is set for between cotton and linen with no steam).
Place a towel on a wooden table then:
Facing the iron horizontally:
1. Start at the top of the transfer. Go back and forth for 30 seconds.
2. Next, move your iron down to the middle of the transfer. Go back and forth for another 30 seconds.
3. Then move your iron to the bottom half and do another 30 seconds.
When done, face your iron vertically then follow the steps below.
1. Right side of transfer up and down for 30 seconds
2. Middle of transfer up and down for 30 seconds
3. Left side of transfer up and down for 30 seconds.
If the transfer sticks there could be one of two reasons.
1. You may need to go over it again
2. You may have a bad transfer (which happened to us, we had a bad batch of 10 transfers).
Good luck. Hope this helps.