Even if the battery charge is too low to crank the engine, if it has the juice to open the doors, the ignition should still come on with lights on the dash. This is likely more than just a battery issue.

 

Was this ever solved? I have the exact same problem on my '14 V6 base. Its intermittent, but I usually have to exit the vehicle, lock it, and unlock it and re-enter to get it to turn on. If I use the fob to lock/unlock within the car it will performs the operation, but it does not allow the car to start. So frustrating. And it's not like when you just don't put your foot on the brake and you hit the start button and it goes to Acc, it just flat out does nothing whether I have the brake pressed or not, as if it ignores that the key is in the car. I've held the fob up to the indent under the dash and it doesn't help either.

 

1. Make certain your battery is fully charged.
2. put a fresh battery in your key fob if it’s more than 3 years old.

 

My key fob battery was replaced very recently, thinking of using the spare and see if that has any affect on it.
I will check the battery, what exactly am I looking for with this? A certain voltage while the car is off?

 

The best way on the battery would be to put it on a charger overnight.

 

The same thing happened to my '19R recently - went to the grocery store and when I came out it wouldn't start. I was able to get it jump started that night and drove home. I then put the charger on it all night long - the next day wouldn't start. Checked it out with my multi-meter and showed 13.8V - figured it should start because everything else seemed to be working. Charged it some more to no avail, but was perplexed because the multi-meter showed plenty of juice. Finally I took the battery in to be tested and it showed a charge, but as soon as they applied a significant load to it, it bonked. New battery and all is good.

 

You have to remove the "surface charge" from a newly charged battery to get a true reading, Jaguar used to (maybe still does) recommend leaving the battery for 24 hours, or to run the headlights for an hour, before rechecking.

In an incident similar to yours on a 2004 XKR I went to buy a new battery and the guy in the shop insisted on testing my battery, claimed it was fine and refused to sell me a new one. I went home and bought one online and had no issues after that, so the load tester isn't always helpful.

 

I guess the point of my post was that even though a battery shows a charge, it doesn't necessarily mean the battery has enough strength to start the car. Just because you test it with a multi-meter and it shows good numbers doesn't necessarily mean the battery has enough strength to start the car. Just because you charge it overnight doesn't necessarily mean the battery has enough strength to start the car. Just because you do a special dance with the key fob and whisper the magic words while holding it in the perfect position doesn't necessarily mean the battery has enough strength to start the car. The point of my post was to point out the most obvious first culprit - the battery. Start there.

 

I had a similar issue last fall (2016 V6S). Some electronics would work, no crank with starter. I couldn't jump from the engine "jump posts" but the electronics worked better when connected to my booster pack. I eventually tried jumping on the battery (on the terminals in the trunk) and it jumped fine. Everything worked fine after replacing the battery. I would try to jump from the battery or just replace the battery. A 5 year old battery is going to need to be replaced any time now (I only got 3 years out of mine and use a trickle charger when stored over winter). A new battery is the cheapest repair here and hopefully the only one. Good luck.