On our 2019 cruise we also arrived early, and Scenic booked us at the Hyatt Regency Nice, a lovely hotel right on the Promenade des Anglais. It seems Scenic has preferred hotels it uses in its destination cities, and this was the one in Nice. That way we also had their transfers from the airport and to the ship, even though we arrived early. Many passengers arrived for the cruise via Marseille, and bused up from there.
On our upcoming trip, which begins in Lyon, they use the Intercontinental Lyon, but we were told their block of rooms was full. We then booked the Intercontinental directly, and pressed Scenic to provide the transfers, and they have agreed to do so.
Perhaps you could try that route. Having the transfers is really helpful.
Like you, I have spent many, many hours on the phone with Scenic trying to make arrangements. Email has not proved helpful. You might try asking the reservation person to put you through to their travel department, they seem to be more knowledgeable. Another wait on hold for them, but they have a call-back feature, and one of them told me they respond to all of those calls the same day (and that has been my experience).
Good luck, and to be continued!