Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
It is possible that the user account got corrupted. That is why it is not logging in to it. We can create a new user account, then recover the files of old user account through root account.
Follow the steps below to create a new User Account in Single User Mode.
• Reboot your Mac
• Immediately hold down the Command(Apple) and S keys together for 10 seconds to boot into Single User Mode
• When you see the text prompt, type in the following terminal commands to create a brand new Admininstrator account (hitting return after each line). Also, note down the spaces between the commands, like a space between mount and -, space between -uw and / etc
mount -uw /
shutdown -h now
After rebooting, you should be able to create a brand new Administrator account. Let me know once you did that, so I will send you instructions to enable root and recover the files from other account.