General:
* Deadlock
* Stalemate
* Standoff
* Gridlock
* Logjam
* Bottleneck
* Roadblock
* Dead end
* Cul-de-sac
More specific:
* Frustration (when referring to a feeling)
* Impasse (when emphasizing a complete lack of progress)
* Inflexibility (when referring to a lack of willingness to compromise)
The best synonym to use will depend on the specific situation and what you want to emphasize.