It's probably saying that the server is blacklisted.
Following instructions are to get around the blacklist:
1. Uninstall current version of GT-MP.
2. Download GT-MP Launcher from here: https://gt-mp.net/download/
3. Once you have installed the GT-MP Launcher, click the launch button to load into the game to install the dependencies and script hook.
4. Go to: C:\Windows\System32\drivers\etc and look for the hosts file.
5. Drag the hosts file to your desktop
6. Open the hosts file with Notepad and add the following line to the end of the file. 127.0.0.1 master.mta-v.net
7. Drag the hosts file back to C:\Windows\System32\drivers\etc
8. Launch the game again and connect to the server with Quick Connect!
How should the hosts file look?
The line above can be added at the bottom of the file. IMAGE: https://i.imgur.com/KYPsaiZ.png
Launcher errors?
These errors can be ignored. The game will launch through it. IMAGE: https://i.imgur.com/gPzE5Y7.png
Server information
IP: play.eclipse-rp.net Port: 7001 (necessary) IMAGE: https://i.imgur.com/3rX25nL.png