You see "Fees Parse Error" if:
your Amazon Seller Account is not connected to Seller Assistant or the extension couldn't get the data from it (the Amazon Seller Account is banned or it's on individual plan). In this case Seller Assistant tries to parse Amazon Revenue Calculator
the extension can't show the data as the error occurred during the parsing process
What to do?
Use VPN while using Seller Assistant (if you are not in the USA)