Space Bar

Is any of the clips on the key cap damaged? Are any of the little nubs/stubs on the key mechanism broken? If none of these items are broken, then you need to determine which way the key cap should be oriented. There is only one direction which will work and if you try to press the key cap into place with the key cap oriented incorrectly you will damage the key cap and possibly the scissor/butterfly mechanism.

You need to make sure the metal stabilizer bars are positioned correctly and pushed to the most extreme upper & lower points respectively. Once you do this and determine the correct key cap orientation you should be able to gently press the key cap down so the scissor/butterfly mechanism snaps into place. You will need to very gently wiggle the key cap to the top and bottom to try to snap the metal stabilizer bars into place as well. If you do this wrong you will damage the key cap and possibly the scissor/butterfly mechanism. See if iFixIt.com has a guide to help you (moderators won't allow me to provide a direct link).

If this laptop uses the dreaded butterfly mechanism, then you need to be extremely careful since if you break the butterfly mechanism it will require a very expensive Top Case/Keyboard Assembly replacement. If it uses a scissor mechanism, then maybe the scissor mechanism and key cap can be purchased online if they are accidentally damaged (I've never looked for the 2020 model).

You may want to have Apple or an Apple Authorized Service Provider examine the key cap and mechanism and to reattach it for you assuming nothing is broken.