If you have trouble activating the theme on a new server, then do check the following:

#1 - Whitelist this URL in your firewall: https://edwiser.org
#2 - CURL PHP extension is installed on your server
#3 - Choose Edwiser RemUI theme as the active theme on your Moodle site and then try activating the theme from Edwiser RemUI settting > License settings.
#4 - You need to use Edwiser RemUI's license key for activation and not the purchase key or another other key for activation
#5 - If you already own Edwiser RemUI PRO and purchased a new Edwiser RemUI starter suite, then to activate Edwiser RemUI starter suite you need to install RemUI starter suite files to activate Edwiser RemUI starter suite License key.
Note: Edwiser RemUI starter suite License key will not work in activating Edwiser RemUI PRO files and vice versa.