Since updating to Power BI Desktop 2.87.684.0 64-bit (November 2020), I can no longer refresh data from Smartsheet or establish a connection to Smartsheet.
On initial refresh or when trying to establish a connection to Smartsheet, I get the message: "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel".
I also get a message that my Smartsheet credentials are not valid (organizational account using Microsoft SSO). From PBI desktop, when I try to sign-in to Smartsheet again or as a different user, I can get as far as allowing PBI to access Smartsheet data, but everything ultimately fails with the message "[Access denied] Power BI is unable to complete the login process".
I am 99% sure this is an issue with Power BI Desktop 2.87.684.0 64-bit (November 2020) as my colleagues are experiencing the same issue. Also datasets pulling on Smartsheet that are published to Power BI Workspaces appear to have no issue connecting to Smartsheet and refreshing their data as expected.
I have tried multiple installs / uninstalls of Power BI from the Microsoft Store as will as a direct download (x64 installer). I can reproduce the issue on multiple machines (professional & personal) and when connected with different networks (corporate, home, and public).