Yesterday Fantastical 3.1 stopped syncing with my Google account. It pops an error message “status code 403”. I was able to shut off Fantastical and grab BusyCal from Setapp, which is syncing fine with Google.
A support email from Fantastical told me the error was global for any app syncing with Google, and has been fixed. Obviously not true on both counts.
So – FYI, if you have this issue it’s likely not a local problem on your machine but something wrong with Fantastical perhaps.