Timing Mark not showing up??

Was the timing light flashing consistently after the marks disappeared?

You could have a bad timing light, bad plug wires, bad distributor cap, fouled plug on number one cylinder (or more), or a weak spark in general.

A few things you could do, in no particular order.

Invest in a multi-meter if you don't have one. Test lights can be of limited value when you're trying to determine if you have (for example) 6 volts versus 9 at the coil. How many volts at the coil when running?

Start the engine, clip the timing light pickup to various different plug wires, then aim it at your hand. Don't worry about which cylinder you're clipped to. Are you getting a consistent flash on some cylinders and not on others? Are you getting a consistent flash on ANY cylinders?

What does the number one plug look like?