The main thing to clarify is that Accept Hosted doesn’t provide complete
SIM feature parity. Customer ID and line-item display may not be
supported on the hosted form, while field requirements need to be
configured through the Accept Hosted request. ...
If the registration is working but the activation URL still fails, it
sounds like an issue on the sandbox service rather than your browser.
I'd report the exact error message, the activation URL (if it doesn't
contain sensitive data), and the time it...
