Hi @passionbull
please ask Heroku, what that means.
Checking your domain you have created two certificates - https://check-your-website.server-daten.de/?q=goodhabit.me#ct-logs
| Issuer | not before | not after | Domain names | LE-Duplicate | next LE |
|---|---|---|---|---|---|
| Let's Encrypt Authority X3 | 2020-04-13 | 2020-07-12 | goodhabit.me - 1 entries | duplicate nr. 2 | |
| Let's Encrypt Authority X3 | 2020-04-11 | 2020-07-10 | goodhabit.me - 1 entries | duplicate nr. 1 |
Last is created today.
So use that certificate.