Contact your ISP (Internet Service Provider)
Maybe there is an issue with your internet connection which is due to the ISP itself (a problem with the ISP's DNS settings or something else), which prevents you from loading any website (or only a certain website).
Call your internet service provider whose team will troubleshoot and resolve the problem as soon as possible.
Maybe the website you are trying to visit is restricted to certain countries other than yours or maybe there is something wrong with your ISP. The first thing you should do is to check whether the website is really down for everybody. Go to Downforeveryoneorjustme and enter the website's URL in the field (e.g. google.com) and press Enter.
If the website is up, you will be able to access it through a proxy server. Check out this list (or this one) which lists the most popular and most secure proxy websites.
If others can access the desired website (or your website) but you, there is a possibility that the hosting server of the website is blocking your IP address, or there is something wrong with your ISP's (Internet Service Provider) settings.
Some website owners do this to prevent users from certain countries/location from accessing the website, or to restrict the number of visits (e.g. You get kicked out if you visit the website more than 10 times per day).
Try to access the website through a proxy website. Famous proxy websites include hide.me,hidemyass.com, proxysite.com. If you are not sure how to use the proxy website, they include video tutorial for that purpose. Please note that this is a short-term solution to your problem.
To fix it long-term, contact your ISP first and then the server admins / hosting provider of the page you're trying to access to check why they are blocking you.