Please check the following:
1) If you recently updated DigiCal you might need to restart your phone first to get it working (by the way, if you are using a version before 1.6.3 please update to the newest version of DigiCal).
2) Do you have developer options enabled in your phone's settings menu? If so please disable it, then remove and re-add the widget back again.
3) Please try another launcher such as Solo Launcher to see if you have the same issue:
Widgets are drawn by the launcher so most widget related issues are due to the inability of the launcher to update the widgets correctly.
1. Delete the widget and create a new widget on your home screen.
2. Restart your phone
3. Switch to another launcher such as Nova launcher or Solo launcher