Cloud Build Failure: Could not open a connection to your authentication agent.

Since last Thursday our Cloud Builds have failed and we see this Error Message:

Could not open a connection to your authentication agent.

We also see the following in the Full Log:

4616: is too old (format 29) to work with client version '1.9.4 (r1740329)' (expects format 31). You need to upgrade the working copy first.
4617: ! postcheckoutstatus failed. svn command failed
4618: Build step 'Execute shell' marked build as failure

Pl share any thoughts/suggestions if you have encountered this error before. Thanks!

 

Exist other post with this error.
https://forum.unity3d.com/threads/build-stopped-working.441772/

I think that the error is because the client svn version is too old in the cloud machines