Failed to install the 9/29/23 update. Microsoft installer error; 1603, fatal error during installation.

You might want to download and install the updater patch.

See https://ttlc.intuit.com/turbotax-support/en-us/help-article/update-products/manually-update-turbotax-windows-software-basic/L3Wf9OPaf_US_en_US

Thanks. Already did, it does not help. I think the link is not the latest updated on 9/29/23.

Another thing to try...Check your Windows OS updates. 

One was issued this last week, and if partially-installed, TTX wont work/update right.

Check for the Windows OS update, and reboot anyhow..

.....then try the TTX update again later