Hi there,
I'm Cherrelyn and I'm here to help.
That error usually isn’t on your side it happens when Outlook’s calendar service can’t complete the connection to Google. Since you already tried different browsers and private mode, it’s likely a temporary sync issue rather than a setting on your account. Waiting a bit and trying again later often clears it up, but if it keeps failing, adding your Google calendar through the subscription (ICS link) method in Outlook is a solid workaround until the direct connection is stable again.
I hope this will help and if you have any question please feel free to ask.
Warm regards,
Cherrelyn