The API key is not tied to an applicationb URL. So, I don't think this caused by the URL change.

Where is your server located ?

Doesn't the URL any affect the API? So then, Is there any requirement that using API?

+) I used api in the Synology Video Station. The API worked until the url was changed, but it did not work after the url was changed.

@ju392769 said:
Doesn't the URL any affect the API?
So then, Is there any requirement that using API?

Servers located in Russia are blocked from accessing TMDb.
https://blog.themoviedb.org/the-movie-database-suspends-access-from-russia-and-belarus-b6a1a96fb35b

If you use Cloudflare as a DNS service (1.1.1.1) this access is extended to other countries
because of what we assume is a Cloudflare error.
Try using Google DNS: 8.8.8.8

So I repeat the Moderator's @superboy97 question:

1 - Where is your server located ? In which country ?

And my question:
2 - What DNS service does your server use ?

+) I used api in the Synology Video Station.
The API worked until the url was changed, but it did not work after the url was changed.

First let's try to solve your Server issue.
Then we will try to resolve your Synology Video Station issue.

Oh, I’m sorry that I make repeat the question.

(First of all, my server is Synology and I have problem only synology video station. I apologize for my mistake to confuse you)

I use synology in South Korea. then, I use the dns provided by the carrier (name is KT)

@ju392769 said:
Oh, I’m sorry that I make repeat the question.
(First of all, my server is Synology and I have problem only synology video station. I apologize for my mistake to confuse you)
I use synology in South Korea.
then, I use the dns provided by the carrier (name is KT)

Some Synology NAS/DS Video users have appeared reporting problems.
One of them said there was an update from Synology.
We don't know yet but it looks like this update came with this issue.
So I suggest getting help from Synology's website.
Synology Support.
https://kb.synology.com/en-my/DSM/help/DSM/SupportCenter/SupportCenter_desc?version=6

See if any of these threads can help solve your problem.

Synology NAS/DS Video Reports

2021-11-09 https://www.themoviedb.org/talk/618ada421cfe3a002a4f89d1
2021-07-21 https://www.themoviedb.org/talk/60f89a1b07e281007d7f3ffe
2021-04-10 https://www.themoviedb.org/talk/60716402dfaae9002b30b85c
2021-02-23 https://www.themoviedb.org/talk/6035201c0d294400405ab8a0
2021-02-17 https://www.themoviedb.org/talk/602ca712db4ed600406bb052
2020-09-01 https://www.themoviedb.org/talk/5f4f012b47c9fb0037742b1c

On the topic
https://www.themoviedb.org/talk/60f89a1b07e281007d7f3ffe#60fd75a9c439c00029f370d5
https://www.themoviedb.org/talk/60716402dfaae9002b30b85c#613c26ecdbf1440062fd16c3
the user got some responses from Synology.

Travis Bell reported the ports used by the servers

Hi @USER, there's only 2 ports that can be used to communicate with TMDB's service.
These are your standard HTTP 80 and HTTPS 443 ports.

If your problem is not similar to any of the above cases, I suggest contacting Synology Support.
https://kb.synology.com/en-my/DSM/help/DSM/SupportCenter/SupportCenter_desc?version=6

Finally, I succeeded. Thank you for your help :)

you are right. it problem has come to DNS I tried changing the DNS by 8.8.8.8. it works

if you look at this Question who live in South Korea, try changing the dns