Contact your ISP through their support contact to request that they remove jazzplus.com from their malicious site blacklist.
Use a VPN to access. This will bypass your ISPs security block.
If your ISP has a security app, go into it and whitelist or allow access to jazzplus.com and segplus.com/jazzplus. For example, for Xfinity users, you can use the Advanced Security settings to “Allow Access” to https://www.segplus.com/utahjazzplus if it shows as being blocked in your Security History.
Try to change your DNS provider in the Chrome web browser settings. This is under Settings Privacy and Security Security Select DNS provider. Change this from the OS (default) and use one of the other selections. Or you can go straight to security settings in Chrome by using this URL in the browser: chrome://settings/security
In a web browser go to https://www.segplus.com/utahjazzplus and if you get a security warning that offers a “Proceed Anyway”, click that and try to access.