Here also some additional detailed information about Outlook/Exchange calendar sync.
Please make also sure that you have enough free memory on your phone. If there is no space to save synced data, it will not take place.
If everything is set correctly up, please proceed as follows:
When it comes to calendar sync, please remember that BC doesn't have its own sync abilities and uses only those provided by Android OS. Therefore the cannot be responsible for any sync issues you may have on the device.
As a first step please make sure, whether the stock calendar app preinstalled on your affected device* has the same problem. If yes, it might be a general sync problem and it could help to remove and re-add the account for sync in your Android OS Settings → Accounts & Sync. Please note that with this step most of the sync issues are indeed solved.
Hint 1: If you use BC on Chromebook, Windows 11 or Google-free Huawei devices, you re-add the account directly in BC→ calendars & task lists → calendars.
If your account is set up correctly and you still are not able to sync, please verify also if the calendar sync is enabled in the account's settings. If not, enable it with the icon provided.
Hint 2: If you don't see the option at all, you will have to install Google Calendar App on some devices.
Please make sure as well that the Android OS is not killing the background processes for the app. You will find a nice device-specific overview here
*excluding Google Calendar app. This app does not rely on Android Sync functions and it is therefore not a good point of reference.
If you experience sync problems with your task lists , you may also want to re-log in with the account. This in BC → calendars & task lists → task lists.
Hint: Please make sure to secure your local and not synced data before you do it, because it may be lost along with the process. You can, for example, export your lists.