This is from fiverr support:
If you are a new user that does not have a Business account:
When you put in an email address that already exists on Fiverr, you will be asked to try and use a different email. Alternatively, you can choose to sign in at the bottom of the page. If you click this option, you will be taken to the Fiverr sign-in page.
Once logged into your Fiverr account, you will be asked whether or not you would like to keep your two Fiverr accounts or if you would like to merge the accounts. If you choose to keep two accounts, you will be asked to replace the existing account’s email (assuming it’s your Business email). Thereafter, you will be redirected to the Join Fiverr Business page.
When clicking on Learn More (to merge the accounts), you will be notified that your personal Fiverr Balance will become “private.” Customers can’t spend private funds in a Business account. The only way to receive the funds back is from Customer Support.
Note: Sellers cannot merge accounts; they are required to have two accounts.