I have a Samsung S5 with a finger print lock.
After so many attempts (5) it locked and asked for an alternate password which, unfortunately, I did not set up.
Now I cant unlock my phone. I called my server and they advised me to go on here.
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I understand how difficult is this situation. I would suggest few options , either you can go for factory reset try this :
This will take you to options where you could find factory reset option. Press volume button to scroll and power to confirm. Unfortunately it will erase up everything.
Or log-in your phone from google account. Hope it helps.
I had this same issue causing major concern I logged into my samsung account, from there down the left side is a list of options one of them is "unlock screen" click that. it opens another window with a big button saying "Unlock" click that and with 5 seconds my phone unlocked.
hope this helps.