lost my physical paper interrail pass

I’m sorry, but paper passes can not be transfer to the app, if you lost it. Only with mobile passes is it possible to get it on a new one. If you have an additional Pass Protection or an insurance, they can take for you the cost of new train tickets. 

Here the help information page of interrail.eu about this topic. 

What should I do if my Pass is lost or stolen? (interrail.eu)

You can also get in touch with customer service (write when you are travelling)

Submit a request – Eurail Knowledge Base