There have been problems this week with TB sending lower-case authentication commands to Yahoo which is expecting them to be upper-case. Some users have dealt with your issue by resetting the password or allowing less-secure apps to access Yahoo and creating an app password:

https://forums.yahoo.net/t5/Account-security/CLIENTBUG-SELECT-command-is-not-valid-in-this-state/td-p/300162

My pw works as expected when logging on to yahoo mail, however, when I use the same (exact) pw to log in to T-bird, my pw entry is rejected as not being correct.

Fwiw, everything was working fine, then I received a prompt to re-enter my pw. Since that time, I have not been able to log into T-Bird. Also, I have lost folders in T-Bird on one account but not the other.

Have changed pw's several times to no avail. fine for Yahoo mail, but not T-Bird.

Amen to the title of this issue, that seems to be the problem?

RBGary said

My pw works as expected when logging on to yahoo mail, however, when I use the same (exact) pw to log in to T-bird, my pw entry is rejected as not being correct. Fwiw, everything was working fine, then I received a prompt to re-enter my pw. Since that time, I have not been able to log into T-Bird. Also, I have lost folders in T-Bird on one account but not the other. Have changed pw's several times to no avail. fine for Yahoo mail, but not T-Bird.

Have you created an app password for TB, and deleted the old password in Tools/Options/Security/Passwords, restarted TB, then entered the new password when prompted? For the lost folders, right-click the account in the Folder Pane, Subscribe, then Refresh and check the folders you wish to download.

Deleted all old pw's as suggested. Entered new pw, still get "clientbug' message. R clicked looking for lost folders for both emails.There was no populating of the folder box for either of email account.

Also, did a complete removal of T-Brid including deleting the program in the files folder.

Used the same pw in the prompt/login box in T-Bird that I use for Yahoo. works fine with yahoo, not accepted with T-Bird.

HAVE FOUND THE ANSWER !!!!!!

Recall some time ago, I had received a message from Yahoo "to make sure that I am using their latest security, be sure that apps that use less security is turned off".

Noodled about in yahoo security, found the above text, moused the off/on screen switch from on to off, now I have regained all of the functionality of T-Bird again.

Pass the word on this self inflicted bug, please.

Gary

Hi Gary I use Sky/Yahoo mail and I have been struggling with this clientbug prob for some time as I cannot use my sky mail account, your solution looks promising but I am a bit baffled, can you tell me where to look in Yahoo security to find the apps security button in order to turn it off, would this be in the settings of my sky/yahoo mail? (I have looked but can't find anything) I do think that a lot of people are suffering this bug from yahoo. Regards Robert.

Go to accounts, account security, turn on "allow apps that use less security" access. This worked for a while for me, now Yahoo/Verizon seems to have put up another roadblock to keep it from functioning full time. Fer instance: I can get into one of my accounts but not the other.

Good luck, you mileage may vary.

Gary

I had the same problem: "(CLIENT BUG) SELECT Command is not valid in this state" What you do is you go to Preferences of Thunderbird -> Settings -> Passwords, Show Paswords, delete the Password of yahoo mailbox. Shutdown Thunderbird, launch again, Yahoo ID asks for password, enter password again, and it loads up all the folders successfully.