That Darn Fox in Shadowlands is a quest that has been bogged down because of a bug. Players have been talking about this on the Blizzard forums since Nov. 27, and the problem has yet to be fixed. The hotfixes acknowledged the quest itself as being able to give quest rewards and the fox pet "Renny," but this is not happening.
We're always updating the game with general implementations and bug fixes. See the latest hotfixes here:
— Blizzard CS - The Americas (@BlizzardCS) November 30, 2020
The issue itself is that players are supposed to follow the fox, get stunned a few times and are then able to pick it up, but this is not the case. Most players are unable to interact with the fox and are unable to pick it up to complete the quest.
That Darn Fox Shadowlands Bug Timeline
As of Dec. 2, the Blizzard team has acknowledged the issue and has said the following.
"We have received multiple reports of this issue and can confirm it is not working as intended. Currently, we do not have a workaround or resolution that can be provided. We apologize for any inconvenience while our developers work as quickly as possible to resolve the issue."
They have told players to still report the issue so that they know if it still exists in the game. Some players have luck picking the fox up but it then disappears. Hopefully, this will be fixed within the next few days.