AFAIK noStrudel does not support NIP-17 while Amethyst does (as well as legacy NIP-04)
Discussion
hmmm nostr:npub1ye5ptcxfyyxl5vjvdjar2ua3f0hynkjzpx552mu5snj3qmx5pzjscpknpr is this why??
Ask him to implement the newer DM spec. It's become quite annoying.
Its hard, and the core logic isn't built well for it. To implement NIP-17 well it requires that the app store a bunch of events and keep some local state ( decrypted text, new messages ) which noStrudel isn't setup to handle right now
Clients like amethyst can do it because they have a local database and store a lot of events