Why do some websites get blocked by hosting providers themselves? There are a few reasons:

Viruses – it is possible that your website was hacked and a malicious code was included somewhere, which caused spreading viruses. It is necessary to locate this unwanted code in the first place and then get rid of viruses to request unblocking of your site;

Phishing – another issue that might be caused by hacking is the appearance of phishing pages. They are designed to be disguised as parts of a safe website and fish out personal data and credit card information of the website visitors;

Exceeding load limits – this usually happens to the users of free web hosting services. Such options have limited functionality and space. Their main advantage is their free access, but free hosting are inconvenient for most businesses;

Spamming – your site can be both sending and receiving side for this one. You can be hacked to spam other websites, or face a spamming attack, which will result in overload. If you were hacked and started to send spam, your site will be blocked;

Illegal content – in each country certain web content is prohibited. If your site violates the laws of your country in any way, a hosting provider can suspend the website.