“An error occurred during a connection to nuzleaf.home.younglogic.net. You are attempting to import a cert with the same issuer/serial as an existing cert, but that is not the same cert.”
Many years ago I battled this problem and had different solutions. Today, I got one that worked for Firefox on Fedora 32.
My IPA server is for HOME.YOUNGLOGIC.NET
My backing store for my default profile in firefox is /home/ayoung/.mozilla/firefox/x4kktanr.default
To see the certificates I have in that store:
$ pwd /home/ayoung/.mozilla/firefox/x4kktanr.default $ certutil -L -d . | grep -i younglogic adam.younglogic.com ,, younglogic.com ,, openshift.younglogic.info ,, nuzleaf.home.younglogic.net ,, Certificate Authority - HOME.YOUNGLOGIC.NET CT,C,
To delete that last one:
certutil -d . -D -n "Certificate Authority - HOME.YOUNGLOGIC.NET
Then restart Firefox. It holds this in some other cache, perhaps memory, until a restart. Note that the file that backs the certificate database is: cert9.db. It is a SQLite database with a very unfriendly schema.