Key mechanism for door not working
 

I would suspect either the key fob has been replaced or the door lock barrel has been replaced.

You can buy replacement key blanks and get it cut to match the door barrel.

https://www.ebay.com.au/sch/i.html?_...c&LH_PrefLoc=2

Thanks for your help
As you suggest, I think I have to get a new key cut!!
it’s very unusual though, as there has been no changes to the door or lock or fob key.
cheers

Do you have the second key fob & emergency key? Does it work?

Unfortunately No
I didn’t want to get another one ( emergency key and electronic fob ) before I knew that the original emergency key I have would work. I will get the key code from my local Mazda dealership and cut another one as you suggest but I am concerned now that the lock mechanism is either faulty or not the one for the car. If I cut a new one it may not work either.
either way I think that I am doomed for a $$ bill!!!
do you think it may be electrical or car battery related?

Highly unlikely to be electrical.

You need to get the barrel removed & the new key coded to it, not the original factory key code, just incase its been replaced.

Okay, I’ll do that and see how it goes
Thanks for your help
I’ll let you know how I go

Problem solved
barrel was full of oxidisation according to the locksmith. After a cleaning out of the barrel I am on the road
cheers for your assistance