Is tail enabled?  There are also application settings for tail which may be worth reviewing.

If you monitor the file in explorer, does the file size grow over time?

Yes, tail is enabled and I also checked the settings.

But when i watch the file in file explorer I see that the KB size does not increase. Apparently the explorer does not update the file size in real time.
In the file itself, however, several (albeit few lines) logs are written per minute

To see the file size change in explorer, you will need to refresh (F5).

LogViewPlus monitors the file size.  If the size is changing, you should see some activity in LogViewPlus.   I just tested and this feature appears to be working.  You are the first customer to highlight this issue.

If you look at the statistics view, are there any changes?  Maybe the file is being tailed, but auto-scroll is disabled?  Have you tried tailing the file in another program, or from the command line?

I have now monitored the logs again with Notepad++ via tail. Even there, entries are not displayed at all or only with a long delay when they change.

Obviously Windows only writes the log file from time to time and keeps the rest (until it is written) in some cache.

Thanks for your help, I think the problem is not with LogViewPlus but with Windows

Thanks for the update.  Glad to hear the issue appears unrelated to LogViewPlus.

I would suggest that it may not a Windows issue, but an issue with how the target application is writing log files.  There may be some kind of caching involved.  If so, you could look for a 'flush logging' option.  That is just a blind guess though, I don't know anything about the target application.