I was having a problem with codesigning my apps, so I deleted all the keys from the keychain. Then I went to Certificate Assistant => Request a certificate from a Certif
After revoking every certificate I had, I figured out the problem was with my yubikey. It was getting in the way of signing the app. After I removed it, problem solved.
This forum thread helped me out: https://forums.developer.apple.com/thread/106938