Question: 
When I have Plauti Deduplicate and Plauti Cloud open on two tabs in the same browser, and I switch between the two, I get errors stating ‘error parsing json response: "unexpected token ‘<’’. logged in?" and then I am logged out of Salesforce.

Answer:
Refreshing the Plauti Deduplicate tab should solve this. If not: either open Plauti Deduplicate and Plauti Cloud in two different browsers, or close the Plauti Deduplicate tab before opening Plauti Cloud.