When you try to upgrade the PRO version of Opening Hours module you'll see: Error connecting to the server: 403
You'll see this error because the PRO version can only be downloaded by subscribers. We developed a plugin to solve this. The plugin will be installed with the Opening Hours PRO version.
Go to plugin manager
Search for the Installer - Opening Hours plugin
Open the Installer - Opening Hours plugin and enter your Download ID
Your Download ID can be found on http://www.joomill-extensions.com and if you login go to your account-page. It looks like:
After you entered your download ID and update the extension the same way as the free version.
When you still see the 403 error, make sure you have entered the right Download ID (Every subscription has his own Download ID #) and you have a active subscription. When your subscription is expired you cannot update the extension.