Sometimes the Permalink structure on WordPress is corrupted.
You can recover from this situation by disabling Redis Object Cache and updating the Permalink structure.
Step 1. Select [Settings] Menu on left sidebar, then click [Redis] menu.
Step 2. Click [Disable Object Cache]
Step 3. Redis Object Cache has been disabled
Step 4. Click [Permalinks] menu then [Save Changes] button without changing anything to force an updated Permalink structure