I have a 2017 Hyundai Elantra leased since March this year. On 2 occasions I put the key in the ignition but it would not let me turn it. What causes that?

This could be caused by the deterioration of this small flexible coupler located in the steering column. The good news is you don't need to have the entire steering column or intermediate shaft replaced as most people think. This tiny, $2.00 flexible coupler and two hours of labor could be the answer to your problem.
Nov 25, 2015

Hyundai / Kia clicking noise in steering column

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2017 Elantra steering "clicking" sound when turning the ...

Reddit https://www.reddit.com > Hyundai > comments > 201...
Dec 27, 2018 - It's the rubber coupler in the steering column. It's not really dangerous or hazardous as the steering still works fine, it's just annoying.

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You need someone with a programming scan tool.

https://www.programyourremote.com/classified/2017-hyundai-elantra-keyless-entry-remote-fob-smart-key-programming-instructions-listing-8720.aspx

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Sounds like a programing problem. Most car accessories are controlled by a pcm or bcm (powertrain control module) or Body control module).. You call it the car computer. Sometimes a spike in voltage or some other abnormality can cause a glitch. Take it to the dealership and have them run a diagnostic and reflash the module.

The OE alarm is part of the ETACS
To disable it:
1) Sound the alarm
2) Put the key in the ignition and turn to start
3) Hold there until the alarm turns off
You should now be able to start the vehicle. The alarm will remain dis-armed until armed through RKE

There is NO kill switch on the 2000 Elantra... HOWEVER, there is a thing called the Key Fob (keyless remote entry system). There is, however, a system in place called the 'starter kill' circuit and it is activated when the burglar alarm goes off.... it's called the burglar alarm relay and it is activated to prevent the engine starter system from being used. There are three ways to get the engine started in such a circumstance... 1. use the key fob to 'disarm' the system... 2. put the key in the ignition and turn it to the 'RUN" position and wait until the alarm stops (horn stops beeping and the parking lights stop flashing), then the engine will start.... 3. pull the starter relay from the UnderHood junction box and bypass the starter circuit (key in ignition and in the 'RUN' position), jumper the starter solenoid circuit to energize the solenoid to start cranking the engine -- it should start then.

This really doesn't help you much, but Hyundai has an awesome feature that won't let you lock your keys in the car. good if your forgetful

Amazing!.. Belts don't 'ignite!' Never have and never will. Find yourself a good mechanic/technician and get them to look at it.

IT could be two things. The first thing it could be is the ignition itself. This type of ignition has a electrical plug that will pop up when the car is put in park so if the car is not in park or n the key will not come out. On elantras these sometimes fail and fail often. When thay do fail the key will get stuck and like you said you can go back later and the key will come out. The problem is that you do want to get a new ing you will have a 2 keys. your old keys for your doors and a new one for your ing cause hyundai will not rekey ingitions. The second thing that it could be is called a park safety switch when you put the shifter in park it sends a signal to the electrical plug to lift up. This sensor is under your shifter and also goes bad often causeing the same problem. These sensors are in the same circuit and are tied together I always replace both.

car should be under warranty .. try having a new key made .if that dosent fix it. it's in the key lock maybe a wire loose .