I have spent the afternoon reading the "How to Debug the EPM Add-in" document and with the users Appdata\Local\Temp\Log folder there us a Log edited at a time we tested the fault , which produced the following info:
2016-05-11 15:22:37,105|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:37,121|ERROR|FPMXLClient|FPMXLClient.ReportManagement.SheetOptions.DeserializeFromXml|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:37,137|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:37,152|ERROR|FPMXLClient|FPMXLClient.ReportManagement.SheetOptions.DeserializeFromXml|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:37,152|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:37,199|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:48,658|ERROR|FPMXLClient|FPMXLClient.ReportManagement.SheetOptions.DeserializeFromXml|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:48,721|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:48,752|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:48,768|ERROR|ReportManagement|FPMXLClient.Office.EPMExcelReportManagerRepository.GetReportManager|user|||||1|Unable to get the Object property of the OLEObject class#
2016-05-11 15:22:48,799|ERROR|ReportManagement|FPMXLClient.ReportManagement.RangeUtil.GetSpecialCells|user|||||1|No cells were found.#
2016-05-11 15:25:29,839|ERROR|ExcelEvents|FPMXLClient.ExcelEvents.xlAppEvents_SheetActivate|user|||||1|Exception from HRESULT: 0x800A01A8#
Does this help? And anything that reads "unable" to me must be a issue?