The only other reference I could find to this type of issue was here: https://moodle.org/mod/forum/discuss.php?d=398209. In that case, it sounds like users were able to login after a few attempts. I'm not sure if you are seeing the same result, but the suggestion in that case was that perhaps there's a third party plugin somehow interfering with the login process.
Failing that, how were the users given their password? For example, are they set using "Generate password and notify user" or manually generated and distributed? If manually, are they being set to "force password change", and if so, are they failing before or after the password is reset by the user?
If the passwords are completely manual and consistently failing for the same users, is it possible the passwords distributed could be incorrect? Perhaps that can be confirmed/ruled out by performing a password reset on one of the users to see if it resolves the issue. If it doesn't, then it could identify that the password itself isn't the cause and this needs further investigation.
Thanks Michael,I appreciate for your quick response.
Yes ,password was manually generated and distributed through SMS. As you said password reset seems working . Third party plugin we installed is "User bulk enrolment v3.8-r2" and as you said it is good idea to try to know if there is related issue due to this plugin.If any one knows that plugin please give me a comment.