Sounds like you're hitting a DNS block of some kind. Known regions that have issues are Russia, Belarus and India. The Indian government has been seen blocking our domain at times. We block Russia and Belarus.

I'm guessing if you were to issue this command:

dig +short api.themoviedb.org

You get something like 127.0.0.1 back?

Sometimes switching your DNS is enough to fix these kinds of issues. You can try switching to one of (test these separately):

• 8.8.8.8 (Google)
• 9.9.9.9 (Quad9)