I just found my twirssi inactive.
When loading the script and authenticating with oath enabled, I got the error:
-!- Irssi: Error in script twirssi:
Timestamp out of bounds
This is (most likely) the result of a wrong system date/time.
Quite easy to solve, just sync it to an NTP server.
Open a terminal and enter:
Try to load the script again and login.
All should be fine now.