Having sync issues, you need to establish, if the accounts are set correctly up. Here you can see how to log in with the account for calendar sync and here you can verify the setup procedure for your task lists. 

Here also some additional detailed information about Outlook/Exchange calendar sync. 

Please make also sure that you have enough free memory on your phone (note that some devices require at least 10 GB to start the syncing process). 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 (unless see: → Hint 1) and uses only those provided by Android OS. Therefore it cannot be responsible for any sync issues you may have on the device. This is also the reason why the reinstalling of our software does not solve the problem.

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. First check is the calendar sync is activated for your account. This in your Android OS Settings → Accounts & Sync. If yes, the next step is to remove and then re-add this account for sync also in your Android OS Settings → Accounts & Sync. Please note that with that particular action most of the sync issues are indeed solved.

Hint 1: If you use BC on Google-free Huawei devices or sync Outlook/Microsoft with our own pro sync, 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 if the calendar sync is enabled in the Business Calendar account 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. Most modern devices restrict the background activity for the apps (very often without informing about it), which can greatly influence the sync process as well. Even if you feel like you didn't change anything in your setting, please don't skip this step. 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.