I tried to split a switched outlet so the top is always hot and the bottom is controlled by the switch. I snapped the brass connector off and wired the neutral (with black tape) to one of the hot leads with a pigtail. The other neutral went to the silver terminal. Turned the circuit back on and now the switch does not control anything and the outlet is always hot. Any advice?

Something is amiss here: NEUTRAL is normally the white wire and HOT is the black wire.

There should be a shorting bar across the tin screw and connected to the original white wire.

The brass screw side of the outlet should have the bar removed. The top outlet should be pigtailed and connected to HOT (original black) and to black of the switch.

The white wire from the switch should be taped black at both ends. The white with black tape from the switch should be connected to the bottom (controlled outlet).

The switch could be bad. Try pulling one wire off it. Do you have a feed pair coming into the outlet, and then another pair to the switch? If so, the feed neutral should connect to the plated screw of the outlet. The hot should be pig tailed to the top brass screw and to one of the wires to the switch. At the switch, one wire should be connected to each screw. Then the other wire is connected to the brass screw on the bottom of the outlet. The white wire between the switch and outlet should be marked black on both ends.

If you have Power to both sides of switch, with switch off, you may have another receptacle
That still has tab on receptacle hot, last remodel had 4 recepticles, that half of outlet was switched.