If the widget is blank or shows the "preparing ..." message
Please wait a few minutes or try a reboot.
Last resort would be to remove and add the widget again.
If you are using a Samsung phone
Samsung is pretty aggressive at putting apps to sleep.
Solution, part 1:
Please check if CalWidget is on the sleeping/disabled apps lists and remove it from there.
Go to the phone's settings, "Battery" (sometimes found under "Device Care"), "Settings" (probably reached via the "..." at the top right).
- check "Sleeping Apps"
- check "Disabled Apps"
If CalWidget is found in any of those lists then please remove it from there.
Solution, part 2:
Go to the phone's settings, choose "Apps", tap the 3 dots "..." in the top right and select "Special access" and "Optimize battery usage" (don't worry, this will not start any optimization).
You will then see a list of all apps and whether they are "optimized" or not. That is Samsung talk for restricting apps to run.
CalWidget should not be optimized, so let's check on that:
Set the list to "All" (default is "Apps not optimized").
Look for "CalWidget" or "Resizable CalWidget" and make sure the toggle is OFF i.e. the toggle is grey and in the left position.