I try to get Mine 75-90% ! You can take the bator into a steam filled HOT bathroom and open the lid. This will quickly increase the humidity. I use a small room heater set to 100 or on high then crank the shower on HOT!!!! when the room is filled with steam I turn off the shower then open the bator. I remove chicks, shells, and add HOT water to the trays. This also works to jump humidity up in a hurry! I also tap on the glass/plastic to imitate the hen pecking around the eggs and I also cheep to the eggs! Some times I will just gently shake the bator just enough to make the eggs move. I think this helps. I believe it just lets them know someone is there and is waiting on them. LOL It usually works! I have NEVER lost a chick do to shrink wrapping! Yes I know your not supposed to open the bator! But this is how I do it and it has always worked!!!!
I have had it take 25 days for a hatch without any problems!
Good luck and God Bless!