My 2014 C5 Tourer has stopped working with the keys

[Lynnzer]

It's about 4 weeks ago that I put new batteries in my keys, including the spare.
Yesterday they stopped working. I can only lock and unlock the car by turning the key in the lock, which obviously negates the alarm system.
I thought at the time that as both keys stopped working it was more likely to be a fault on the receiver in the car, or whatever it is that picks the key transmission up.
I had a new battery installed today at a local auto accessories shop and it still doesn't work, so it appears that this is a fault in the electrical system or something.
Anybody know how I might fix this? Could it be reset by a diagnostic check, perhaps/

[GiveMeABreak]

You need to reinitialise the fobs after replacing the batteries.

1) Get both fobs, sit in the car
2) First fob, place in ignition and turn the accessories only position, then press the fob lock button for 2 seconds, then turn ignition off (do not start the vehicle).
3) Repeat for the second fob.
4) Exit car and attempt remote locking and unlocking with fob 1, repeat for fob 2.

If this doesn't work, make sure you have the correct coin cell battery type in the fob - they are not all the same and should be the CR0523 type.
Edit: Looks like another Owner's Handbook Error and CR1620 are perfect.

[Lynnzer]

Batteries OK on both.
Tried the reinitialise but nothing gained.
Like I said, the batteries were changed a few weeks ago with CR1620's which is what I have always used. They worked fine, or at least the main one did as I had no need to use the spare.
Then one day last week the main key stopped working, although I tried it later in the day and it worked again for a few hours. I tried the spare key that had the CR1620 inserted and that wasn't connecting.
It was then that I went to an auto spares shop who fitted another CR1620 after looking at the one already there. He said that the one I had fitted was a typical pack of 4 purchase from a supermarket, and he was correct in that.
Anyway, as both keys had become inactive I put it down to a receiver problem and that seems to be the case as the reinitialise did nothing.
Is there an easy way to have that checked out and what sort of cost would a new one be?

[wheeler]

Sorry if this might seem obvious but these are things i have seen too many times before.
Are the batteries the correct way around? I checked a key for someone just last week who had taken their remote into timpsons for a new battery & they had just fitted it the wrong way around. I have also seen people fit these batteries that are still wrapped in plastic or have stickers on them believe it or not.
If the batteries are ok & correctly fitted you ideally want to check that they are both transmitting a signal, most garages should have a basic signal tester. Do you have diagbox? You can see if the HF receiver is seeing the remotes, the HF receiver is integral to the comms unit (indicator & wiper stalk assembly) I would say the failure of the HF receiver is quite rare.
If it was me i would try re programming the keys then doing the re sync procedure, this sometimes does the trick. You would need your 4 digit security code & a diagnostic device that can code keys.

[Lynnzer]

I've checked the battery installation, and in fact have one key with the battery installed opposite to the other one which may have shown one of them to be working, and the other still dysfunctional. So whatever it is, isn't batteries.
I've just been up to an auto electric garage and he checked the keys on his device that picks up any signal at all, and there's nothing showing for either key.
This seems really odd. So the keys look to be knackered. I guess it'll need new ones, but 1st I'll try the CR0523 batteries mentioned in the 1st response. It seems really strange that the batteries used right now, the CR1620's, are the same ones that have always been in the keys for the past 3 years,

[GiveMeABreak]

Ignore what I said earlier (I'll correct that), I think they made another error in the user handbooks (not the first time), I've checked parts and there are 2 references, an original and a superseded part, but both point to CR1620 Lithium batteries, so don't waste time on that.