Model S locked out

[Caterman]

6 month old Model S - Tried to open it this morning and it was completely unresponsive to either key or app (but I could put on the climate and vent)
Phoned Tesla, they managed to unlock remotely, tried a reset and it would now lock and unlock on the app but nothing on the keys (and I had replaced one of the batteries by then as well)
Advised that the keys were not connected to the car, would need to be reconnected which is only possible at a service centre.
Any ideas on the cause, is it a "thing", can't see anything on the internet.
Fortunately (?) it's due for its 3rd service visit in 6 months and 2000 miles this week so I can get it done at the same time

 

[pgkevet]

That's not one I've come across as a problem although my S has been telling me my fob battery is low despite putting in two difference new brands that i had lying about.. granted they may have been old stock when i bought them a year ago and a new order hasn't arrived yet to try. Since it happened shortly after an update I wonder if there has been some attempt to reduce readable range??
There was (is?) a fob update routine amongst the car's menus that may be worth trying if it still exists. I did it to both fobs about a year or so ago when it became available.

 

[Caterman]

Thanks for the idea, tried the fob update and it says it can't detect a key even though it is placed correctly as per the diagram.
I wonder if it is a sensor problem as logging in to the tesla app it takes a few seconds to wake the car up and this evening on returning to the car at a shop I was left stuck outside the car for 5 minutes while the app tried to connect with the car.

 

[Caterman]

Just to wrap this up (sort of), after a frustrating week of using the app to drive the car culminated in me in the rain with my 89 year old mum with dodgy knees waiting for 5 minutes for the app to connect (model S uses phone signal rather than the model 3 bluetooth), Tesla St Andrews Birmingham took pity on me and I spent the afternoon of my Friday holiday having the keys sorted out..
The outcome was the keys were fine and a reset of the security controller allowed them to work although rather worryingly the invoice says "Can't be sure why this happened" so I'm left with the thought "when will this happen again?"
PS I must apologise to the lady at the Digbeth service station about the rather bizzare and rather fraught conversation she had with a lunatic who hadn't realised his appointment was at the other Tesla Birmingham!

 

[pgkevet]

I finally sourced a new Panasonic battery for my fob with 9 years shelf life remaining, but car still tells me fob battery is low. I need to get round to doing the same with wife's fob but starting to suspect that the last update has had some bug effect on how the car senses fob power cos I can unlock the car with the fob from 40 yards way (haven't tried farther)