If there is not state reporting requirement, boxes 15, 16 and 17 will be blank.
If Box 15 and 16 are filled, then you should reconfirm with your employer on Box 17 - they should have withheld some state income tax which should be reflected under Box 17. If nothing has been withheld, then it should have stated 0.00 and this is what you would enter on your taxes (and you would have to pay state taxes at the time of filing).

What if i worked in CA and know I paid state taxes? The w-2 i got was hand written by my previous employer but she no longer owns the business

Boxes 15 through 20 are State/local taxes. If there is not anything listed then you do not need to enter anything.  If tax was not withheld the box will be blank. However, if you know taxes were withheld you may want to contact your employer to get a corrected W-2. There are certain instances where state taxes are not withheld, in those instances the box/boxes would be blank..

My w2 is blank on line 17. The state keeps rejected my taxes. What should I do?

Leave boxes 15, 16 and 17 blank on the W-2 since there is no amount entered in box 17.