I appreciate the time you took to report this to us, Kai.
QuickBooks has country-specific versions, and regional restrictions may apply. Since your client is in the US, please ensure you sign up using the US version.
If you’ve signed up under the Philippines version, you’ll need to create a new account in the US version.
You can check this article to know more about what to do if invited users did not receive your email invitation in QuickBooks Online.
You can revisit this thread if you have further concerns about your QuickBooks invitations.
