edited 12/09/19 in API & Developers

I have an application that updates a SmartSheet using the available APIs.. The application uses the C# NuGet packages for Visual Studio (2017)

The program has been working flawlessly for over 12months now but as of 1am last night (UK time), I no longer am able to connect getting the very basic error of "There was an issue connecting"

After grabbing the code for the library from GitHub I managed to ascertain that actual error was "The request was aborted: Could not create SSL/TLS secure channel."

Further googling suggested that this could be a TLS issue and now added TLS1.2 connectivity.

Did anything happen with TLS protocols last night?





  • We have 3 different services that use the Smartsheet API that stopped working at 8PM eastern (1am UK). This feels like more than a coincidence.

    We are troubleshooting on our side as Smartsheet hasn't reported any changes.  

  • Lily Seifu
    edited 12/07/18

    We also had the same problem.  We were using PowerShell to get sheets and added 

    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

    to the script and it fixed the problem.


  • Hello All,

    On November 30th, we deprecated support for TLS 1.0 in order to maintain the security of the Smartsheet API.

    As Lily suggested below, including TLS 1.2 to your script will fix the issue. (I believe that you can include TLS 1.1 or higher but 1.2 is a more secure option.)

    It's likely that your script didn't need to perform a TLS handshake until recently so you're only seeing the problem now.

    I think the most common scenario is when a TLS 1.0 script notices that the MD5/SHA cert has expired, requests a new one, then our API denies the request due to the deprecated TLS.

  • This worked for me too, but it had to be implemented today on 4/3/2019.