You need to grant access to user1 using it's IP to access the remote server:
GRANT ALL PRIVILEGES ON database1.* to 'user1'@'xxx.xxx.xxx.xxx' IDENTIFIED BY 'pass1';
NOTE: replace the relevant info to the current info such as
xxx.xxx.xxx.xxx to the current server IP that will access the remote MySQL.
Since you're using cPanel you can do this to allow the IP:
- Login to your cPanel (if not already logged in).
- Scroll down to the Databases section.
- Click on the Remote MySQL icon.
- Enter the IP address of the computer that will be making the remote connection.
- Click the Add Host button.