My MacBook Air 2020 won’t turn On

If it is an Intel Mac, then I would not recommend spending any money on repairs for multiple reasons. Due to the design of these 2018+ Macs, it is very difficult, sometimes even impossible to determine exactly which part is bad without swapping in a known good part. Without seeing the laptop I'd say there is a 50/50 chance of a problem with the Display as Apple mentioned, or the Logic Board.

If you haven't used this laptop much, then most likely you let the battery drain to 0% for extended periods of time which has most likely damaged the battery.....besides Lithium batteries start needing to be replaced at around 3 - 5 years anyway. FYI, you need to make sure to always keep the battery charged between 20% - 80% when storing the laptop.....make sure the laptop is powered off when stored. Also, disconnect all external devices prior to powering off the laptop since connecting/disconnecting items, even the power adapter can cause the laptop to power back on. Also avoid touching any keys or even the Trackpad since that can also power the laptop back on. I don't know how long it would take for the battery to drain from 80% down to 20% where you would need to charge it again.

Besides the future of Macs are the M-series Macs. In my opinion, money spent on repairing an Intel Mac is better put towards a new laptop.

It is only required if the Apple service diagnostics show a battery failure. In fact Apple won't even consider replacing the battery unless it fails the diagnostic and/or shows a "Service Recommended" battery condition. Apple repairs everything or nothing at all.

I just wanted to mention a possible near future repair cost. There is nothing worse than spending lots of money on a repair only to find out you are paying for another repair later on.

Edit: You can find out the battery repair price by looking at this Apple article:

Mac Repair and Service - Apple Support

Of course if Apple determines the battery needs replaced during the repair of the laptop for the display issue, then the price may be different for the battery replacement. It also matters how Apple or the AASP is performing the repair (sometimes they just do a mail-in repair while other times they replace individual parts in the store/shop).