Authentication aborted - no supported schemes

I’m currently using eMClient with a free licence, intending to upgrade to Pro if it seems to be working OK. But… it’s not.

For some reason, it’s unable to connect to my main IMAP server. The settings are correct (verified and re-verified just to be sure), but I’m getting an error saying that the authenticaion is aborted. Here’s an extract from the logs:

17:15:39.286|001|   eM Client 9.2.2093+6d2fe6bf90 (Windows)
17:15:39.287|3B6|   Account's UID is b561320d-4bf5-4936-9c90-be9e50906f10
17:15:39.287|3B6|   AccountBase.ChangeOnlineState : State changed to ONLINE due User
17:15:39.288|3B6|   >>> ListFoldersAsync(): Start
17:15:39.288|3B6|   01:   Connecting to ##########...
17:15:39.290|3B6|   >>> FolderActivated(folder: /Inbox [Inbox]): 
17:15:39.290|3B6|   Folder /Inbox [Inbox] is now watched
17:15:39.299|3B6|   01: * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS LOGINDISABLED] Dovecot (Ubuntu) ready.
17:15:39.300|3B6|   >>> ConnectionPoolEntry.CloseAsync(): Failed to connect: MailClient.Accounts.ConnectionException: Authentication aborted because none of the schemes announced by server () is supported.

(The server identity is redacted, but it is correct, I can assure you).

Any suggestions as to what the issue is? Thunderbird is connecting to the server without any issues, and I can connect manually via telnet, so there doesn’t seem to be a server-side problem. The server is running Dovecot, and is the current version.

Many thanks for any help that anyone can offer!