Recently while trying to set up Unified Routing, we got the below error.
“Unified routing was unable to provision. Please try again or contact Microsoft Support”
The user had the system administrator role and we already had the global administrator’s consent, which should be good enough to set up unified routing.
We tried with different system administrator users but that doesn’t resolve that error.
Eventually, we tried the setup with the same user but in a different VDI (Virtual Desktop Infrastructure), and the setup worked properly without any error. One probable reason could be, that the appropriate URLs being accessed during setup were already whitelisted in the other VDI, which wasn’t the case in the first VDI where we were trying.
Hope it helps..
Nishant Rana's Weblog 
Hi Nishant, thank you for this troubleshooting steps. I couldnt turn on with your suggested however I tried with the steps that I documented here which worked for me. Sharing the same here for your perusal. – https://sharanlakkani.wordpress.com/2022/10/20/troubleshooting-unified-routing-was-unable-to-provision/
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