After a number of years of being offline, we recently brought our message board back from the dead. Some of our users/members couldn't remember their old logins and just re-registered as new members. Is there a way to merge an old member account with the new user/member account?

Yes, you can merge members in ACP while viewing their profile:

 

From the guide:

Quote

• Account Actions - This is where you will find the option to merge the account with another, or delete the account entirely. Of note however you can also download the members personal information should this be requested by the member, and also use the 'Log in as...' function. This can be helpful if you need to diagnose an issue while logged in as that user.

You can also choose which account is kept and which is deleted after the merge.

Edited September 26, 20231 yr by teraßyte

You can indeed. Visit one account in the admin CP, click on account actions, and you will see "Merge with another member"

EDIT: Terabyte beat me to it 😄 

Excellent, thank you.