I got a Schwab manager by the throat and finally got a real answer to this issue. They claim that the various versions of TT have changed how data is transferred over the years and the only version of the interface that they keep online is the version for the current year. As a result Schwab customers today can access their data through TT only for 2022 and 2021. I tried 2020 and 2019 and both fail. Schwab is unwilling to have more that one transfer interface operational on their systems so the versions that existed for previous years are currently disabled even though the forms for as many as 10 years are online in pdf, xml, and csv format.
Frankly, this is a poor answer. Amending returns is not uncommon and the IRS can go back as many as 6 years in an audit. Even if it is seldom used a respectable brokerage firm can support previous versions for 6 years if they want to. They just don't want to. Thanks to TT folks for their attention to this matter.
