Problems installing new pushrods!

Your lifters have just bleed down...

Try to pump them back up manually - remove one at a time (or mark which position they came out of) and then cut an old oil container to be about 3" taller than the lifter... Put the lifter in it and fill it with oil until the lifter is completely submerged.... Then use one of the push rods to press the plunger down and see if any air bubbles come up... Keep cycling the lifter plunger until it "stiffens up"... Then reinstall and adjust...