We are unable to process your request. An unknown error occurred.

I have been trying to enrol in the Developer Program, however, I keep getting an error message which reads 'We are unable to process your request. An unknown error occurred.' I have tried to reach out via the contact us channel, but phone calls are not being accepted and I have emailed twice with no response. The information presented says that someone will be in touch within 1-2 business days but that hasn't been the case. What can I do to proceed to the next stage?