PMOs are quite vulnerable within organizational setup. There are many reasons behind this. Over last so many years of direct and hands on experience across many industries and countries we have developed great insights of what works and what doesn't. Most importantly, what causes PMOs to fail? Let's think of some reasons below,

• Lack of empowerment
• Lack of sponsorship
• Lack of organisatinoal support and focus
• Lack of support from project, portfolio and program management resources
• Changes to business strategy
• Changes to business structure and processes
• Staff turnover and lack of stability
• Status quo
• Stalemate
• Competence of project management resources
• Lack of training, awareness and efforts to connect PMO with managers
• Static and outdated measures
• etc... 

While almost every organization face totally new and different blend of issues with PMO efficacy but these are couple of common ones.

PMOs run well for some time, typically 2 - 5 years after they are setup and then they fade fast and eventually become useless. PMOs that is why should be put efforts on to keep relevant so that company's goals are efficiently achieved.

Let us know what you think are other common reasons of PMO failures you can think of or experienced?