No flash, bullets look worn/dirty/ rusty?
Clean them. Pull them out of the loop, pull the wire out of the loop.
Wires out of the bullets. Do the test again directly at the wires. The tool flashes?
Wonderful. Clean the loops, clean the bullets an fit again. Put the bulb in, it must flash.
If no flash at the wires. Short them and test again. No flash?
Look at the connector in the wing. Unconnect it. Test the connector from the car. Put a needle in one hole and cramp it with the tool. The other hole hit with the tools needle. The tool flashes?
Than the problem is in the connector or the wire to the indicator. The tool doesn‘t flash? The problem ist in the connector.
Usual Procedere in all british cars.
Greets René