Sometimes, a weak or unstable internet connection can cause Outlook to misbehave. To check if this is the issue, temporarily disconnect from your Wi-Fi or unplug your LAN cable, and then try opening Outlook again. If you receive a connectivity error, your network might be to blame. You can also connect to a different Wi-Fi source to see if that resolves the problem. Method 8: Repair the Corrupt PST File Using SCANPST.EXE ...