Will not go into EV mode

For starters you need to take it back to the dealer if you just bought it because they will have a warranty on it that would cover this even if the OEM warranty has run out. Clearly you don't want to delay that so that you don't have any out of pocket expenses.

Next this could be a number of things but the most common and unfortunately the most expensive is the hybrid battery is discharged to the point it needs to be replaced. The EV system will not engage if the overall state of charge of this battery is too low. We need to use a scan tool capable of monitoring the battery to see what the charge level is.

https://www.2carpros.com/articles/hybrid-battery-information

If the battery is ok then we need to check for codes. If there is a DTC the EV system will be disabled. They don't want to risk switching to EV mode if there is an issue and it also forces the customer to get the vehicle repaired.

So let's check for codes and go from there.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here is a guide for just some more info on hybrid vehicles if you are interested:

https://www.2carpros.com/articles/hybrid-motor-and-transmission-information

Take it back to the dealer! It could be a simple issue, or a complex and expensive one. I know because I am the only one at my dealer that works on these.