Actually...its not two account with the same UserID...it's two Deductible accounts with the same Email address on file.
It might be easier this year to just enter your Deductions directly in the TurboTax Tax software without using ITsDeductible at all. There are a bunch of problems with it this year.
IF you had an ITsDeductible UserID that you historically used....but that UserID was different from your tax account....then what you entered may have been into a new ItsDeductible account that had the same UserID as your tax account......(but I can only guess at what you actually did)...no, you cannot combine accounts.
....for Online Software Users:
While the early releases of the software appear to indicate that you can import ItsDeductible data from an account with a different UserID, that is currently not available and may not be allowed this year.
Going forward, should you decide to continue to use ItsDeductible, I would encourage you to only record your ItsDeductible donations in an account that has the same UserID as your tax account.
Unfortunately, this is going to cause you extra manual entry work this year, putting your donations directly into the tax software, unless you want to wait a month or two to see if TTX developers or management decide to fix the foul-up....no promises that they will.
(Desktop software users do not have this limitation)