macbook air 2020 suddenly not charging

First, read If your Mac battery won't charge - Apple Support.

If none of that helps perhaps the power adapter and / or cable may be defective. Depending on your model MacBook, read

If your MagSafe cable or power adapter isn't working - Apple Support

If your USB-C power adapter isn't charging your Mac notebook - Apple Support

If the battery has been left in a discharged state for a long time, it may need to be replaced: Find how to service or repair your Mac.

Also make sure the outlet you are plugged into has power to it.