If a replay link isn't working, you can enter the Battle ID directly inside the game to watch a specific match. Please follow these steps to do so:
Step 1: Get the Battle ID from the replay link. This is the alphanumeric code written after q= on the link.
Step 2: On Classic, go to the Menu and click the Battle Logs button.
Step 3: Click the search button on top of the battle logs.
Step 4: Enter the Battle ID and click View.
After entering the Battle ID, the match replay will then start to play.