Currently (as of V13r3 latest) if a user locks himself out of myApps by repeatedly entering a wrong password and is thus blocked for a certain time from signing in, the block time can not be reset by any means.
If a user is blocked for a long time, he simply has to wait for the block time to count down to zero.

There should be an administrative way to unlock a blocked user and reset the block period, e.g. via the users admin app.

Best Regards

Danny