Doublecheck that you have QA Checker enabled (check box set) in the Project Settings...

...and that you have not excluded the segment type(s) which you actually WANT to check:

And are you triggering the verification manually (by pressing F8) or expecting it to be triggered automatically in editor?

The thing is that in editor it's triggered only if you manually confirm the segment by pressing Alt-+. It's NOT triggered by simply moving the cursor to next segment, or setting the segment status e.g. using the context menu, etc.

Unknown said:

Try unchecking "Report all non-excluded segments" in the "Segments to Exclude" options. It's at the bottom. If you uncheck this then it works fine and all your errors are correctly picked up.

Huh, but that doesn't sound like correct functionality of that option, does it?

In fact I'm not really able to decipher its meaning. The option itself, including the description in the dialog, and its description in the help are so cryptically worded that I simply don't understand what is it supposed to do...

EDIT:
The below is my understanding of the settings. If my understanding is correct, then the entire settings section/dialog is VERY confusing, given the fact that it's called Segments to Exclude and the fact that all the settings with various and sometimes contradicting meanings are all placed inside the same Segments to Exclude groupbox.

It all seems to work as actually intended in the end... just the GUI and its wording is confusing. It dates back to at least QA Checker 2.0 in Trados 2007 (couldn't check the QA Checker in Trados 7.x as its settings didn't want to open due to some missing DLL in my test install).
If the GUI gets fixed - i.e. options grouped to correctly named group boxes and the settings pane named appropriately, reflecting the fact that it does NOT concern only exclusions - everything will be pretty much fine, IMO.
Yes, the problem is that even a small change incurs additional work/costs (help, documentation, etc... and all that in multiple languages), but it all tracks back to not doing things properly right at the beginning and letting them unfinished. The minimal savings back then just add up and multiply over the years to way bigger spendings later.

A quick idea, not necessarily perfect:

It all seems to work as actually intended in the end... just the GUI and its wording is confusing. It dates back to at least QA Checker 2.0 in Trados 2007 (couldn't check the QA Checker in Trados 7.x as its settings didn't want to open due to some missing DLL in my test install).
If the GUI gets fixed - i.e. options grouped to correctly named group boxes and the settings pane named appropriately, reflecting the fact that it does NOT concern only exclusions - everything will be pretty much fine, IMO.
Yes, the problem is that even a small change incurs additional work/costs (help, documentation, etc... and all that in multiple languages), but it all tracks back to not doing things properly right at the beginning and letting them unfinished. The minimal savings back then just add up and multiply over the years to way bigger spendings later.

A quick idea, not necessarily perfect: