Umbraco Backoffice Login stop working suddenly

Question

I am using UmbracoCMS 7.6.2 in one of my site.

Today when I tried to login in Umbraco backoffice using mysite/umbraco, will my working credential, it shows me error:

Answer 1

it finally working.

I've change the useLegacyEncoding="false" to true and it starts working normally.