Different rail companies have different rules regarding night trains and what type of pass you need to travel in a specific type cabin.

ÖBB allows you to travel in any type of night train cabin with a 2nd class pass. Swedish SJ requires a 1st class pass for 1st class cabins and Swedish VY don't allow Interrail/Eurail travellers in 1st class night train cabins at all. So it varies from company to company. 

Excelsior cabins in Italy aren't available for rail pass holder at all, even not for 1st class rail pass holder. So the information is correct; you can't use your pass for this.

But it would have been possible to head to Messina (just about 40 to 60 minutes from Taormina depending on train) by regional train (no reservation needed). The trains from Palermo to Roma have availability for rail pass holder tomorrow (there's no Excelsior sleeper on this part of the train); would have been cheaper and easy to do. And it's the same arrival time as it's just one train from Messina.

If you want to try the passholder reservation from Palermo, as above, you might be able to get a refund on the tickets you just purchased.

A BASE ticket from Trenitalia, for example, you can cancel for an 80% refund.

So it’s a big cancellation fee, but possible.

Thank you for your answers! Good idea to change trains in Messina but it wasn’t an option in our case travelling with small children.

We ended up having a terrible night in the Excelsior Class  I have travelled on many night trains, in all types of classes but this was by far the worst experience ever. I started a new forum thread about that if you are interested.

 Thank you for your answers! Good idea to change trains in Messina but it wasn’t an option in our case travelling with small children.

We ended up having a terrible night in the Excelsior Class  I have travelled on many night trains, in all types of classes but this was by far the worst experience ever. I started a new forum thread about that if you are interested.