safari cannot open page, what to do?

Follow troubleshooting steps given these articles.

https://support.apple.com/en-us/HT204098

https://support.apple.com/guide/safari/if-you-cant-open-a-website-ibrw1071/mac

This is not an unusual complaint. Web site engineers write their software to work with specific browsers and specific versions of them. For some reason, they often choose to not be compliant with Safari. This is not an Apple problem as Apple has no control over the millions of web sites on the internet. You can hope that your web site's developers eventually update their site to work with Safari, or you can use another browser that does work, such as Firefox or Chrome. Sometimes, by upgrading your computer's operating system, which also updates Safari, it will work fine with the offending web site.

Reload the page and try again.