Can’t log in anymore: "Invalid output size / Invalid username, password or backup string"

[davidfoerster]

Since yesterday I can’t log into Threema using Pidgin with threepl any longer. Whenever I try I get a pop-up dialogue:

• Window title: Login Error
• Message title: Invalid output size
• Message: Invalid username, password or backup string
• Available buttons: close

Considering that I changed none of my log-in data recently I doubt that that’s the actual issue.

• Pidgin and libpurple version: 2.14.10
• ceema/threepl version: 8f2d466

Pidgin’s debug log contains nothing of relevance regarding the log-in process:

(18:25:14) account: Connecting to account XXXXXXXX.
(18:25:14) connection: Connecting. gc = 0x5611e8f83160
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) blist: Updating buddy status for XXXXXXXX (Threema)
(18:25:14) pidgin-encryption: Using pre-existing menu icon for conv 0x5611e69a2d90, win 0x5611e89d2a20, item 0x5611e87116f0
(18:25:14) pidgin-libnotify: Conversation Updated (UNSEEN)

Any idea what might be wrong?