Solved: Backblaze does not back up the “Documents” folder

You don’t see the Documents folder under Exclusions in your Backblaze settings, but it’s missing from View/Restore Files?

Open Terminal.
Run cat /Library/Backblaze.bzpkg/bzdata/bzexcluderules_mandatory.xml

It’ll show you the cause of the issue. In my case, the end of the output of the command looked like this:

<!-- Dynamic folders such as DropBox 
are added programmatically 
in BzMandatoryExclusionRules::allRules -->

<!-- Sync.app -->
<excludefname_rule 
plat="mac" 
osVers="*"
ruleIsOptional="f" 
skipFirstCharThenStartsWith="*" 
contains_1="/Users/myusername/Documents/" 
contains_2="*" 
doesNotContain="*" 
endsWith="*" 
hasFileExtension="*" />

</bzexclusions>

My backup returned to normal after I uninstalled Sync.com.