I presume you used the marelli tester to reset the air bag controller? If you use it, you can go through the built-in diagnostics to try to pinpoint the problem. Did you recently pass through 100K miles give or take with the car?
The machanic used a hand held device, with an Alfa Romeo logo, to triage and reset the air bag warning indicator. I can find out if it was a marelli tester. The car is about to turn 188k miles, with no other issues to report. After the clock spring and air bag light were reset, about 3 weeks had past before the warning indicator came on again.