What was the time span from when you created your token and it stopped working? I’m not sure if this setting will affect bulk invite tokens, but the default for user invite tokens is 30 days. I haven’t used bulk invitations, so I don’t know if there is a separate expiry time which will override this or not.
/admin/site_settings/category/users
invite expiry days 30
How long user invitation keys are valid, in days