We have had, in the past, some access problems by users from China and India.
Some Android users also had access problems due to security protocol issues.
So, it would be good for you to provide more information.
In wich country are you
What is your Operating System
What is your Mobile
Who is your Access Provider
And what else do you suppose is relevant.

Does this thread help?
https://www.themoviedb.org/talk/5c3928d70e0a26444200460f
Otherwise, more detail would be needed.
Country, ISP (Internet Service Provider), Firewall, etc...

If you’re in China, we’re having trouble accessing the API Server.
https://viewdns.info/chinesefirewall/?domain=api.themoviedb.org
Look here:
https://www.themoviedb.org/talk/5e53e694a93d25001a4ce468
https://www.themoviedb.org/talk/5e521f1fa93d2500134a0374

And see here https://www.themoviedb.org/talk/5e987f2fb339030015a2743c

Hi I am from India and I am using Airtel as my network provider. The strange things I have noticed

1. themoviedb.org works with other network provider like vodafone and few others.
2. I am using one plus as my device.
3. themoviedb.org works on my laptop only if I connect my laptop with hotspot (Connected with Airtel Hotspot)
4. themoviedb.org gives me error on my development tool(Android studio) when I run it on real device : java.net.UnknownHostException: Unable to resolve host "api.themoviedb.org": No address associated with hostname
5. api.themoviedb.org with the API calls return perfect response if I run it on my android emulator which is connect with the hotspot of the same Airtel network provider.
6. To ensure more on this I tried ping this as well and I saw I am getting the perfect ping on this website as well.
7. I am fairly sure this is the issue related to network provider since I am using your APIs from quite a long for my android apps for POC. I have spoken to the Network Provider but due to lockdown they gonna take time to reply me back with the proper answers. I have crossed check with few of my friends who has the same network provider and non of them able to access the website.

So the bottom line for all of this is, themoviedb.org only works if I am using my app on the emulator. it does not work on the real device and throws the error mentioned above. On the real device it only works if I use VPN on my mobile device.

I'm not a programmer or a connection specialist.
I'm just curious about this area. :-)
Since your case appears to be a mix of Android and India,
it may be that the issue of TLS or SSL is interfering.
( https://www.themoviedb.org/talk/5e987f2fb339030015a2743c )
Anyway, I suggest you post that description of your comment there in the topic regarding the question of India.
( https://www.themoviedb.org/talk/5c3928d70e0a26444200460f )
Maybe you can get more technical help there.
Or create a new one, but with a very meaningful title.
India, connection, android, vpn etc ...
Sorry I can't help anymore.

There's been some of reports of TMDb being blocked on a few ISP's in India. Airtel seems to be the common link I've seen so far. Are you using Airtel @vishvendu?

Yes I do use Airtel and I have spoken to their team for the same, they accepted the problem is from their side and they asked me to wait for few days . I will update you once I get any response from them related to this.