Hello and welcome to the forums first of all.
Goto this link to see if your fob is the problem.
By the sounds of it it is as mine does the same. iirc you can't get any old fob and have it coded. It has to be a new one. Unfortunately these can only be bought from a dealer
which costs £80 approx. renault charge £50 approx. to code it to your car. Any auto-lock specialist can code it, however, even they have to go through Renault to get the fob still. I have tried, ha.
You don't need a new key blade as you can use the existing one. Some fobs can be repaired too. If you think it is the button the maybe going to an auto=lock specialist can help and just fix it. If it doesn't work though, you need to goto Renault.