MySQL replication 'connecting to master'
If you have validated the credentials you are using for replication and they work connecting through another client, your 1045 error may lie with the new default authentication plugin in MySQL8. When trying to connect with an insecure connection and an account created with the caching_sha2_password, it will continuously attempt the connection without being successful.

Try connecting using the same replication credentials from the slave to the master through a MySQL client. This will ensure your networking and credentials are both valid. If you cannot do this, check your network/firewall and your replication credentials.