password problems

Move your content to a new Mac was used ?

Reset Computer Password 

Intel Computer

1 - Restart computer and immediately hold Command + r keys

2 - Top Tool Bar >> Utilities >> Terminal

3 - Type resetpassword as one word and no spaces

4 - Press Return key

5 - Follow the prompts and remember the New Password

Apple Silicon M1 Computer 

1 - Choose Apple menu > > Shut Down.

2 - Press and hold the power button on your Mac until you see “Loading startup options.”

3 - Click Options, then click Continue. 

4 - Top Tool Bar >> Utilities >> Terminal

5 - Type resetpassword as one word and no spaces

6 - Press Return key

7 - Follow the prompts and remember the New Password

Try:

https://support.apple.com/en-us/HT202860

Was Migration Assist used to do exactly that. Migrated Everything from Old Computer to New Computer? If so, it may have also brought over the Old Account too.

Welcome and thank you too.

Do come back to the ASC Forums if or when additional issues may arise