Check if you have proper connectivity to the backend database.
Check SQL server specified in the Topology is functional.
Try starting the CSPool using Skype for Business Server Management Shell.
Start-CsPool frontendpool.testexchange.biz (If things are ok – It will start of)
You can get clue if there is any issues – like below .
Verify these groups have “Public” Permission on SQL Servers. If its a Always ON cluster . make sure it exist on both of them.
Worst Case – Try do a full reset on CSPoolRegistrarState . Note : Do it only for Fresh deployments. As it requires a DB rebuild.
Reset-CsPoolRegistrarState -PoolFqdn frontendpool.testexchange.biz -ResetType Fullreset