Can't Sign in and play multiplayer

I experienced this issue in version 1.21.90.23, where multiplayer was unavailable and signing in took a very long time. It was fixed in the next update, 1.21.90.25, but signing in still takes a long time. After updating to 1.21.90.26, signing in became impossible unless I went to the Marketplace—which I think causes even more issues with signing in. When trying to join someone’s world, it won’t let me and just shows the image I uploaded. Please fix this as soon as possible.