Post-purchase upsell: invalid token on calculateChangeset

[mashkovtsev]

I'm trying to set up a post-purchase upsell.

I submit all required fields to the calculateChangeset function, but the request returns an "Invalid token" message. API_KEY and SECRET are correct. Also, the API key in the Chrome extension is equal to the API key in my extension .env. Are there any additional reasons why requests may be rejected? 

Thank you.