There are only shell change notifications appearing there, which are a secondary type only used to update icons and a few other things. Detecting new files and most other events relies on a more general type of change events.
Those more general events aren't appearing at all in the log, which suggests a problem somewhere in the system.
We've seen anti-virus/anti-ransomware software do this in some circumstances, especially with OneDrive and Documents folders, where they decide they don't trust a process and won't let it see events about what's happening. (There's also at least one antivirus which breaks rename notifications due to a bug, but even with that people still saw a lot of other events.)
Some things to check to work out what's going wrong:
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What happens if you show the Desktop folder in Opus, and create a file there with another tool (not the same screenshot tool)?
Does the file appear in Opus? Is the problem restricted to the OneDrive folder/sub-folders, or to files created with the screenshot tool?
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If other software is looking at that OneDrive screenshots folder, can it see the files being created by the screenshot tool?
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If you run the ChangeTest program linked near the bottom of the guide, does it report any change events, or is it not getting them either?
(Note that ChangeTest.exe only monitors C:\ by default, although you can tell it to monitor other drives. A test on C:\ should be enough to tell if the general notification system is working or not.)