I used VNR to read Watashi ga Suki nara "Suki" tte Itte! full version and it worked fine. I don't remember if it needed an H-code or not but you can find out through the side bar. Bring up the side bar by hovering over it and go to Menu---> Text Settings. Once you are in text settings, click the H-code box and use the drop down menu to see if any codes were entered recently. If so, select the H-code and then click save.
I read Flyable Heart ages ago. I think I used a partial machine translation patch that was available.
And for anybody else not getting text from a game. Make sure you use the side bar and go to Menu ----> Text Settings and see if any text is showing up. If you are not getting text, minimize the Text window and click through the game a few times to advance the text. Sometimes with VNR if you don't minimize the text window before clicking through the game, VNR will not show all available text threaeds. You may also need to check the H-code tab and see if anybody has entered any H-code. Sometimes VNR won't always use the H-code for a game when you first start it up. If anybody has entered an H-code recently it may show up in the drop down box. If you are getting text make sure to set the proper window to "Dialogue" then hit save. Next go to Options using the side bar and make sure "Machine Translation" is selected. Finally, if you want to use Translation Aggregator in tandem with VNR make sure copy to clipboard is selected. TA and VNR with show different translations even with the same translators because they use different scripts. This can be useful because sometimes the older scripts work better.
I never play full screen but if I remember correctly you have to run the game as admin and also run VNR as admin. If you dont run BOTH as admin, it will break various features of VNR. For example VNR won't even see the games exe and will fail to hook any text.
Sorry if you can't make sense of any of this, I'm not really great at answering technical questions. I hope it helps though. VNR can be a pain to learn to use but once you figure it out it does a great job translating VN's.