Already done that. Tried all service-accounts with these permission settings.
Still getting "access denied"-error:
[bucketHash:9D064CD6] Unable to load list https://intranet.com/customer/issuetracking/Lists/Tasks/MyOpenTasks.aspx due to acccess denied error. Exception details follow. Type: 'System.UnauthorizedAccessException', message: 'Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))' and stack trace:
at Microsoft.SharePoint.SPGlobal.HandleUnauthorizedAccessException(UnauthorizedAccessException ex)
at Microsoft.SharePoint.Library.SPRequest.MapUrlToListAndView(String bstrUrl, String bstrUrlToMap, Guid& pgListId, Guid& pgViewId)
at Microsoft.SharePoint.SPWeb.GetListFromWebPartPageUrl(String pageUrl)
at Microsoft.Office.Server.WorkManagement.ProviderOM.SharePointTaskAggregationUtilities.TaskCollector`3.<>c__DisplayClass56.<TryExecuteActionWithListLoaded>b__53(SPWeb web)
at Microsoft.Office.Server.WorkManagement.ProviderOM.SharePointTaskAggregationUtilities.TaskCollector`3.TryExecuteActionWithListLoaded(Func`1 fnGetCreateSite, Func`2 fnCreateWeb, Func`2 fnGetList, Func`1 fnGetListId, Action`3 toExecute).
I googled this error, but with no result. It seems a very specific problem.
Perhaps HTTPS ?