Tabular not able to connect to DB

Tabular giving message that it can’t connect to DB on starting Tabular.xlsm.

Here are the things you can check in this case:
1. Is Microsoft SQL Server Compact 4.0 SP1 installed?
2. Have you unzipped before starting Tabular.xlsm (starting from the archiving program won’t work)
3. Have you unzipped Tabular workbook in a place you have full read/write access.
4. Is the ProgramData/Tabular.sdf file unblocked? (right click properties -> there should not be an Unblock button)
5. In some environments the Antivirus program is blocking the communication between Tabular and its DB. To check if this is the problem stop your antivirus program/service and check if Tabular will run. If yes so there is a conflict with the Antivirus.
6. If you are using Microsoft Sync center to cache your network drive for work offline, sometimes it might misbehave and block the database. To fix just stop/pause the sync or check in it for conflicts and resolve them. Restart of the PC can also help.