I have been unable to access all the seller forums, only Announcements and Technical Issues and all bookmarks and subscriptions have gone.
Etsy has this announcement at top of the forum page ... have you seen it?
Announcement: Starting March 26, you’ll need to be signed in to view most posts in the Forums. Read our post to get more details. Learn more.
This happened to a lot of people after Etsy switched the forum over on the 26th to you had to be signed in to view everything. Etsy said they are working on fixing it. Yesterday there was a mod that was facilitating getting sellers back into the forums if they added their name to the end of the thread. Don't know if that will happen today.
Edited to add: https://community.etsy.com/t5/Technical-Issues/Cant-access-seller-s-forum-Etsy-devs-fix-it-please/m-...