current operation on inbox did not succeed
I've tried Toad-Hall's solution as well as various solutions laid out in https://forums.yahoo.net/t5/Account-security/CLIENTBUG-SELECT-command-is-not-valid-in-this-state/m-p/300263#M24086
None of these are working. This worked fine yesterday (16 Feb 18). Today - only my Yahoo accounts aren't working in Thunderbird.
Opaite Mbohovái (1)
There is no solution. The problem is with Yahoo. Complain to Yahoo.