Windows

Method 1. Log viewer

Use the Log viewer, developed by Acronis Forum MVP, to quickly access the details of the latest backup run, as well as other program logs: https://kb.acronis.com/content/59335

Method 2. Locate and open the log files

1. Navigate to:
   Windows XP: C:\Documents and Settings\All Users\Application Data\Acronis\TrueImageHome\Logs
   Windows Vista/7/8/10: C:\ProgramData\Acronis\TrueImageHome\Logs
2. Sort the logs by date modified (descending).
3. Select the log for the respective operation for the appropriate date:
   service_[date-time].log - Backup/Restore operation
   console-[GUID].log - Operations in GUI
   afcdpsrv.log, NSB_[date-time].log - Nonstop Backup
   tools_[date-time].log - Tools and utilities operations
   MediaBuilder-[GUID].log - Media Builder operations
   installer-[GUID] - MSI installation log

Mac

Method 1. Viewing backup logs through the Console app

Using Console as log viewer is convenient as it gives quick access to all other logs that may be related and useful in troubleshooting: e.g. system logs.
 

1. Launch the native macOS app for viewing logs of the system and from applications. You can find it either under Applications - Utilities, or using the Spotlight search: click the magnifying glass at the right top corner, type Console, press Return
   
2. Once in Console app, expand the section /Library/Logs. Do not confuse it with ~/Library/Logs
3. Navigate to Acronis - ti_demon
4. Tree items with names, starting with ti_demon_ represent backup runs history (backup logs)
   
5. Logs' file names also include the date and time of when the backup task was started
6. Look throught the offered list or see just the most recent ti_demon_ items to review the backup history or find the details of a backup failure

Method 2. Locating backup log files in Finder

Backup log files are written in plain text files which can be viewed in any text viewer or editor.

1. Open Finder window or select Go - Go to Folder... from the top menu
   
2. Navigate to /Library/Logs/Acronis/ti_demon or paste the path into "Go to the folder" field, click Go to open the folder
   
3. Files with names, starting with ti_demon_ represent backup runs history (backup logs)
   
4. Logs' file names also include the date and time of when the backup task was started
5. Sort the files by date or name
6. Look throught the most recent files to review the backup history or find the details of a backup failure. Log files are in plain text format and can be viewed in any text viewer or editor.
   

Analyzing logs

1. A backup log starts with the product and task info:
   <?xml version="1.0" encoding="UTF-8" ?>
   <log uuid="AB05C254-CAD6-4751-AF9A-2C3BD5A473E5" product="True Image" version="18.0" build="5539" task="375880D2-AE15-4F4E-A7E1-5611FF669B72" task_name="Test" >
2. Then operations are listed:
   <event id="1" level="2" module="100" code="2" time="1412956537" message="Operation Test started manually." />
   <event id="2" level="2" module="100" code="0" time="1412956537" message="Operation description: Stage Description." />
   <event id="3" level="2" module="316" code="0" time="1412956538" message="Operation: backup“ />
3. Then service information goes, just ignore it:
   <event id="6" level="2" module="515" code="0" time="1412956540" message="k:\5539\network\astorage\client\address_resolver.cpp:81: DNS resolved: cloud-fes-eu1.acronis.com -> 85.25.240.173" />
4. Find the text error message
   <event id="98" level="4" module="23" code="2065" time="1412956544" message="Nothing to back up." line_tag="0xC4A6B3A72E37E56E" >
5. <event id="103" level="4" module="316" code="5" time="1412956544" message="Operation has completed with errors." line_tag="0x9F2C53C72E8BCDDE" >
6. Interpret the log, search the KB for error message and line tag.

More information

Collecting SnapAPI logs
Collecting Scheduler log
Collecting MSI log. If the standard procedure fails, check in the %TEMP% folder for AcronisTrueImage.msi.txt