@Jeffrey Getts , The Seamless SSO function still resides in Azure AD under the Azure AD Connect blade as shown in the screenshot in the doc. Also the AzureADSSO.psd1 file resides under "C:\Program Files"\Microsoft Azure Active Directory Connect\AzureADSSO.psd1".
It would be great if you can let us know which version of AD Connect is installed in your server. For me in my lab its Version 1.4.18.0 and the latest available version is 1.4.38.0.
I would recommend you using the lastest AD Connect version i.e 1.4.38.0. This version is to be downloaded and installed. This version cannot be auto-upgraded. Also, this version contains a bug fix for the AzureADSSO.psd1 module. Hence getting this module would help you with a clean build of the AzureADSSO.psd1 file.
You can download the lastest version of AD Connect from: https://www.microsoft.com/en-us/download/details.aspx?id=47594
More details about this version can be found here: https://learn.microsoft.com/en-us/azure/active-directory/hybrid/reference-connect-version-history#14380
Do let me know if this helped. In case the the steps helped in answering your query, please mark this response as answered as that it helps others in the community too.