oscommerce website says... "Unable to connect to database server!"

I have 2 Oscommerce sites. When they were setup in 2013, they both had the same "admin name" for each database. It's not been a problem until recently. Now instead of both sites loading one says... "Unable to connect to database server!" So my host made a change and it was resolved, but then the other site goes down and visa versa. Need someone who can make the database change please.