Possibilities:
1) You were using the Desktop software those other years. The Online software does not know about any filings using the Desktop software...even though e-files go "thru" the TTX servers.
or
2) You did use the Online software for those earlier year, but You've logged into a different/new UserID account now. In order to see those prior year tax files, it is critical that you log into your TTX account using the same account Every year. IF you log into a different account, then that new account does not see that you filed in prior years....because you are in the wrong place. Find your other account and log in there.
Follow these directions to find a (make sure you are entirely logged out of any TTX account first):
https://ttlc.intuit.com/community/account-management/help/how-many-turbotax-accounts-do-i-have/00/26...
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*