① The network line used by the user is out of order, resulting in the page that the user browses without network connection.

② The server side of the software may be blocked, resulting in users not being able to use the software normally.

③ It may be because fewer users access the software, and the product is forced to be removed from the shelf.

④ There may be too few users using the software, or the software version is too low. It has stopped working.