How to revive a sourdough starter, Can you?

Hi I am new to this site and a newbie at baking bread.  I am trying to create a starter and the method I am using is from here.

I am up to day three and my starter has NOT risen.  Is there such a thing as a dead starter and can one revive same say with a few grains of yeast or apple cider vinegar to lower the ph.

OR AM I,  just impatient?  The temperature in my kitchen is between 70 and 75 F.

Can someone guide me in the right direction please.

Thanks GregT