Obsidian Entertainment's co-founder and current CEO Feargus Urquhart said that there were a few projects that were pitched by Obsidian but never saw the light of day. One of these games was an RPG set in The Walking Dead universe.
According to Urquhart, the game never managed to get past the pitching phase due to a lack of interest from publishers. We don't know when the idea was floating around, but there were other projects that Obsidian considered but couldn't get off the ground.
One such game was tied to Rick and Morty, which, if you think about current events, might have been a good bullet dodged for Obsidian.
Obsidian appears to have a stacked calendar for the next couple of years, having just released Grounded recently and looking towards it's next big RPG Avowed, it is interesting to know they once had other games in the pipeline, but few are going to be clamouring for that Walking Dead RPG.