Make sure you follow all of the steps in the FAQ. Did you fully update Windows?
This is usually a firewall or windows update issue and the following guide gives a step by step guide:
Hold'Em Manager 2 FAQs - Poker Software :: Can not Connect / Failed to Start PostgreSQL
If you continue to have problems, please duplicate the issue and send us log files with a detailed description of what you were doing and what problems you were experiencing:
- Open Windows Event Viewer's (Control Panel > System & Security > Administrative Tools or Start > Search > 'Event Viewer') > Windows Logs > Applications.
- Check for any errors and send the information (Save All Events As...).
- Please send your \HM2Logs folder files as well -
Hold'Em Manager 2 FAQs - Poker Software :: How Do I Send a Log File to Holdem Manager Support?
When sending any files please zip them (right-click > send to > compressed folder) before attaching them to an email. If the attachment is larger than 10MB please upload them to a file hosting site like dropbox, then right-click > 'copy public link' and paste the download link directly into the support ticket email. If you have any problems with dropbox try using filedropper.com