I forgot the password for my 2015 MacBook Pro

You will now have to change your password to a new, different password. Use the link below to do this. Also, this time write the information down and save it in a secure location so you will have it the next time you need it.

Change or reset the password of a macOS user account - Apple Support

Check out this guide to troubleshoot the issue: https://support.apple.com/en-us/102633