Here's the English version of the DB COVID-19 info page, including cancellation info and links to the order lookup page mentioned above.
https://www.bahn.com/en/view/home/he...NA-Teaser_LZ01
I just converted my super-saver tickets into vouchers good for 3 years. The process was instantaneous.
I mailed them the paper ticket I purchased from DB which included travel on a now cancelled Bernina Express. I previously found a form I could use for that. Hopefully they will eventually process it. Not sure where to request a refund for the seat reservation for the Bernina Express so I tried the contact form on rhb.ch
-David