Western companies who are trying to break into the Chinese market are usually forced to adapt to a new way of doing business, where they would need to comply with the regulations laid out by the Chinese government which can be very different from what they might be used to in the west.
It is one of the reasons why many tech companies from the US have not managed to successfully penetrate the Chinese market, such as Facebook and Google. Microsoft had some success where its Bing search engine continued to operate in the country, or at least until recently where the company confirmed that Bing is now no longer accessible.
According to reports, it is said to be due to a DNS corruption issue which apparently is one of the more common ways that the Chinese government bans websites in the country. It is unclear what Microsoft will do next, but they said that they will be “exploring its next steps”. It is unclear why the ban had suddenly come into effect, but we wouldn’t be surprised if the trade war between the US and China might have played a role.
It is also not the first time that Microsoft’s products have run into difficulty in the country. A couple of years ago Skype was suddenly pulled from app stores in China, once again without any official statement or reasoning.
UPDATE: it's confirmed to be DNS corruption, the common method of banning websites in China pic.twitter.com/GIlYsCVa1L
— Patrick Wu (@patrick330602) January 23, 2019