This famous login redirection (assuming that you use the correct password and username) can have a lot of causes.

Usually the problem is with some plugin that needs to be deactivated, a theme with strange code that refers to hidden cookies, absence of certain definitions in wp-config, etc.

In my case the problem was in the cache and cookies of my browser(s).

I emptied the cache and deleted all cookies, then WordPress accepted my login credentials and I was able at last to enter the dashboard of my blog!