Good to hear - thanks for confirming.

Please enable logging (Configure > Options) and restart PT4.
Play a short session and then attach a Support Bundle to a Support Ticket so that we can take a look at your logs and see what is going on.
Tutorial: Creating a Support Bundle

Checking ('X') is not a common action preflop since it only applies to a player who posted the big blind (or a BB out of position), but it is valid.

The effective stack for each player is based on their first opportunity to act on the relevant street. The effective stack is the amount that player could potentially lose (or win from any other individual player) at that point. It is the lower value when comparing your stack and the deepest stack s...

When installing manually we recommend v10 for PT4.

If you're having trouble with the installation please open a Support Ticket and one of our support technicians will work with you to get you up and running.

When you get a batch of them like that they are older hands at tables that are no longer open. Observed hands will only be imported for new hands that play after you start the import. They are only to allow the Hud to show for table selection purposes. PokerStars only allow us to import 30 observed ...

Those descriptions appear to be the opposite way round to the columns in question, but... Any bet or raise is an "open", and preflop that includes a call when that is the first voluntary money/chips in the pot. If the BB checks then the action is 'X'. There is no 'L' action, only F(old), X...

Please update to PT4 v4.16.2 from the PT4 Download Page if you didn't already.

If you have the problem with that version please do submit your crash report as that is very useful to the development team.
Please also open a Support Ticket so that we can get back to you with any updates.

Are you installing PostgreSQL manually, or is PT4 installing it for you?
Assuming you're trying to install manually, what version are you installing?

When I import those files I can see all of the hands. Please post a screenshot of the complete PT4 window as suggested so that we can see if there are any filters enabled, or anything else that might prevent them showing for you.