I use 6 email accounts with my K9 app. All had several folders besides Inbox. Since I upgraded to version 6.801 for Android, only 2 of these accounts show any folder except Inbox. I’ll lose important data if I can’t retrieve at least the Drafts folder.
[assuming imap] i think that the implication is that you’re not being seen as logged into the accounts in question. try going through that process:
settings/[account/]fetching mail/incoming server/next
watch for any any errors that show after selecting “next”.