Many moments of political expression on social media networks fail to transform into online movements. However, studies on these failures and their causes are conspicuously absent in the literature. We had the opportunity to follow such failure when a contentious policy advocating for the decriminalization of sex work failed to materialize into a cohesive online movement. However, uncovering the reasons behind this failure proved challenging: Why didn’t mobilization happen despite favorable political opportunity structures? Eventually, we turned to existing research on what motivates movement participation and the role of grievances. Shared understandings of grievances are essential for social movements to emerge and sustain over time. However, the focus on grievance formation has taken the back seat in research on contemporary movements and collective action. Through our interpretation of the sex worker policy protest and examining existing research on online movements, we advance propositions of the challenges involved in online grievance formation. The propositions contribute to the pursuit of a theory to explain failure in online movements.