No database instace in nopcommerce v3.90

Hello, I have problem with v3.90. When i edit connection string in Setting.txt file to use my local db, i access my website normally. But, when i use hosting connection string,  i can't connect to my website and error "No database instace". Can you help me, where i can check problem about connect or how to fix this error.
Thank you very much

If connection string correct then make sure your hosting database is accesible from outside that machine.

I've already ping, telnet to my hosting db, it's normally, but i can't apply it to my web by connectionstring. So, i try this connectiong string to nopcommerce v4.30, it can do well.
But i don't want to use asp.net core for my web.
Please help me where a i can find solution for my problem.

What do you mean aki.yuki wrote:
The v4.3 website would not have run using the v3.9 database ?
Have you looked in the error logs C:\inetpub\logs or Windows Events logs

Yidna wrote:
It's mean i can use my hosting connection string if i apply it in json file in nopcommerce v4.30. But when i use this hosting connection string in  setting.txt file v3.90, it show "No database instance" error.

post your connection string here  (with dummy info for db,user,pwd)