As I said, if the same key pair is used, the connection would've been established and the older connection kicked out. Here, no connection can be established in the first place, hinting at a local issue instead. That's why I stepped in to correct you. It's nothing personal.
Other VPN providers also don't offer exact per-key pair control of DNS lists, DDNS entries, forwarded ports and other features (port forwarding is even on the decline with others). There is much sense in doing this manually instead of relying on automations for this. It's not really comparable.
Issues often sound similar, but rarely have the same cause. It's been shown time and time again in the past, so understanding this is essential. The swiftest indicator for whether either of us was right is the system report with the logs.