After updated macOS tahoe, photoshop 2020 is not working.

If you mean photoshop elements 2020, I'm not surprised. it hasn't been updated in 5 years. You will most likely have to upgrade to a supported product.

https://roaringapps.com is a good resource for checking application compatibility when considering upgrading your OS.

Update your Adobe Photoshop application using the Creative Cloud app. The current version is v26.10 and it runs fine on macOS 26 Tahoe.

Edit: Thanks, KiltedTim. If you're using Photoshop Elements (not stated in your post and a different application than Photoshop), then you'll almost certainly need to purchase a new version.

You can try asking in the Adobe PS Elements forum.