I also did the indicated procedure and was able to update to the latest AdGuard Home version. The problem came when I updated the router firmware, enabling AdGuard Home the connection was blocked. I then followed the procedure indicated but could not get it working, so the only solution I could follow was to reset the router and reset the firmware.
I hope for a solution as soon as possible, especially for update AdGuard as the latest versions fix several bugs, including security bugs.