A lot of centralised exchanges come and go And a good example here is Btcdo. This exchange platform is Hong kong-based and was built in 2018 before going down in 2019 following an upgrade which they initially started but were never able to finish. Before the imminent collapse of these exchange platform they had some services which were worth noting and due to this upgrade they provided multiple application support of which unfortunately none are currently working.
A good place to search and know more of an exchange as I have discovered lately is the community groups for which I saw a telegram group for the exchange. I decided to join and see if I could communicate to people but the messaging function was disabled and the administrators have abandoned the group which inadvertently shows that they have also abandoned the work being made to create the Btcdo exchange. There appears to be no hope for the exchange to come back online