Take the burner and flame spreader off of the affected ring.
Look in and you'll see a nut with a tiny hole in it.
Use a thin needle to clear the hole.
Be careful not to enlarge the hole, just clean it out.
Refit the flame spreader and burner cap.
Try the hob again.
If still no gas it would suggest the gas valve for that ring is the cause of the problem.
Hope this helps
Let me know how it goes or if you need more help
OK, you didn't say you'd tried cleaning the jet.
However, as you have, it narrows the fault down to the valve that controls the gas to that ring.
I can't advise on how to change this valve, for legal reasons.
I can only advise that you have a Gas Safe Registered engineer carry out the repair.
I'm really sorry but the law does prevent me advising if you have to break into a gas line.
The problem lies with the jet.
Clean the jet out.
Just clear the hole in the jet.
You are able to buy replacement jets.
They screw in.
Sorry, I really can't advise on this part.
The jet needs cleaning.
How you clean it is down to you.
I can't advise you on how to repair your gas appliance if it involves breaking a gas connection.
You are nearly there though.
A socket would be handy.
Good luck with it.
Sorry, I'll send this as an answer, it will allow you access to the Accept button.
Good luck with the repair.