ADM password not working on htc one m8. Locked out of phone

[AC Question]

hi, I had to use android device manager to lock my phone as Ithought I had lost it. Since found it, the password which I know to be correct is not unlocking my phone for adm. I have tried setting a new password using adm but still no luck. Does anybody know how I can solve this issue, I do not want to factory reset. Have google solved what appears to be a common fault?