Thanks for sharing the relative information.
First of all we would recommend you to use latest version of the API that is 3.7.0
For the point 2 i point out that the example viewer groupdocs-java-client sdk
Can you please share link of this example viewer?
However, using the license file you provided, we are not able to reproduce the issue at our end, it works fine.
license seems that doesn't work (Groupdocs total is correct ?)
Yes, license file is correct.
when i use renderDocumentAsHtml i see a lots of null pointer exception
We are not facing any such exception, we rendered a lot of documents (with different formats) into Html. Can you please provide the problematic file/document? Also, please tell, do you face Null pointer exception for any specific or all documents/files? Let us share some resources for your comfort:
Please go through the above mentioned resources and share your experience.