Confirm that the fund is set to "No Virtual Account" or that the user has access to the appropriate virtual account:
1. Navigate to Control>Administration>Organization Setup>Setup Funds/Donor Designations
2. Hover over your fund name and select Edit
3. Select Virtual Accounts
4. Select No Virtual Accounts and Finish

If this area is grayed out, remove the Campaign from the Fund temporarily:
1. Navigate to Control>Campaign Manager
2. Select the campaign name and choose Properties
3. Select Edit in the Funds Column and make the appropriate fund "Cannot be related to this campaign"
4. Select Finish