This happened to me a couple of months ago where my battery was nearly completely drained because it sat in my garage without running for a couple of days. I charged the battery and took it to my dealership where they said the battery was defective and they replaced it.
It just happened to me again today and I got the message that there was a smart key malfunction and the car would not start. Again the car has sat in the garage without running for a couple of days. Searching for this issue, I've found many other reports of similar issues with 2020 Toyota vehicles. I am currently charging my battery again and have yet another appointment to have my car serviced at the dealership. Upon speaking with a service advisor at the dealership to setup my appointment, he said he believes there is a computer update that needs to be applied to the car. Apparently, there are systems that continue to run even while the car is off, that drain the battery over the course of a couple of days. If you drive everyday, you probably won't encounter this problem until your battery is nearly shot. If you let your car sit for a couple of days, whatever is still running electrically in the car continues to drain the battery until you don't have enough power to turn over the engine. According to my service advisor, the "patch" for the computer system is supposed to alleviate this issue. I'll report back after my visit with the dealership tomorrow.
