On Smeg SRV et all range hobs earthing is an issue with the thermocouples. Spillage usually causes a poor earth which leads to the idea that the thermocouple/s are faulty when all it is is a poor earth. In other words, like most machines, if you’re careless with these hobs they will have their own back by not working as you’ve screwed it up.
That said, thermocouples being goosed is not exactly out of the ordinary.
Depends on the model, the range and if the thermocouples have been replaced as, IIRC, there’s a mod on these.
In any event, like most things gas related, it’s not a job I’d recommend to DIY it.
K.