Sometimes the basic solution is really a simple task and we forget to apply a simple solution. I have the same scenario, the server is working properly and for no reason it stop printing reports again.

Well to make the story short, I've checked my server drive C and D disk space. The drive D is plenty of space to write, close to 100Gb. The drive C is close to 500Mb only but still plenty of space to write. I decided to delete old installer files, temp files, internet temporary files and other junks in drive C. It turns out, another 2GB+ more disk space for my drive C. I've check the printing of report, it works.

I don't know the exact disk space needed for the Actuate Report Server to run but I will keep this in mind.