I've had problems with Jaksta with most sites including youtube etc. I've also seen that there are problems with macOS. I stumbled into a site that works, it is the entertainment tonight site. All others I tried still don't work.
I have attached the log file. I hope this can lead to a solution to being able to use the other sites.
It looks like your attachment didn't work, perhaps try again?
In case your log file is too large to attach, you can drag it into the trash and then Quit and restart Jaksta. It will create a fresh new log file. You can then visit a couple of videos that exhibit problems for Jaksta and then send us the log file.
Here is another try to send the log file.