Display MoreDelta04 if you did do anything from this manual: LetsEncrypt - SSL certificate is not valid
you have to revert changes you've made with 5th point. Otherwise you will get invalid SSL.
Then you have to do this: LetsEncrypt - SSL certificate is not valid
Then go to domain - Let's Encrypt and try to renew certificate. It should not be invalid anymore.
If you will still have problems, you have to get newer SSL certs within /usr/share/ca-certificates (for some reason I've got that issue on 1 out of 5 servers with Ubuntu 18.04) and put them there, then again do dpkg-reconfigure ca-certificates .
sgumbert probably they're set on Domain list as "Invalid", then you have to follow this what I've written in this post above.
theqkash thanks! That worked for me