Update - I am running Studio 2018.4.3. I have uninstalled several packages
(usually in C:\Users<username>.nuget\packages)
and reinstall the most recent packages:
Then getting a conflict conflict with 1: UiPath –
I updated that to version 19.4
I no longer get the “Response from server is not valid” error.
But I do get a new error message now:
System.ArgumentException: You are calling the Computer Vision server too often. 
Apparently there is some limit to the frequency of how often the Computer Vision server can be called and when the activity has a problem identifying the screen it make more calls to its server.
Re-selecting & assigning optimal anchors to each CV activity are helping this situation.