Hello ohero,
Thanks for asking the Apple Support Communities for help with a specific webpage having issues in Safari. We're happy to help.
Please start with the info and troubleshooting here: If Safari on Mac doesn't open a webpage or isn’t working as expected - Apple Support
If the issues continue, check with the web developers to see if their page is even compatible with Safari, as some pages still require other browser. In that instance, you will need to use another browser such as Google Chrome or Mozilla Firefox.
If the above does not help and the developers confirm the page should work with Safari, please let us know and we can check your other settings if they can't help provide those settings. Thanks.