@akahn Thanks for your reply.
It is indeed possible that there is some rate limiting or IP blocking. I initially found that there isn’t a specific Netlify IP range. From your reply, I understand that there is actually one now. Would it be possible to know what are the three possible IP addresses from which the requests are coming from? It would definitely help confirm or discard the possible IP blocking root cause.
I’ve also asked our provider about your suggestion to get in touch directly with you.