I came across this issue. I was able to resolve this issue.
I remember I had renamed the Bot name. I also believe after this change I was not able to get access to studio.
I opened the .json file. Checked for the name attribute. It was the outdated name. So , I updated the name attribute to the latest one. In this I was able to solve this issue.
The version for me was 2018.3.1 This worked for me.
Best,
Sachin