If they accepted service and were an authorized agent to do so on behalf of the corporation, after 30 days you can move the court for a default judgment.
In regards to suing a government agency, you will need to comply with the government code which has very specific requirements that you need to meet before filing a lawsuit.
It is best you contact an attorney who sues government entities to navigate the complex procedural rules.
This is not legal advice and does not create an attorney-client relationship. This is not legal advice, it is only legal information. You should consult an attorney if you have any questions regarding this matter.
I would like a little more information. Specifically, is the non-profit a corporation? If so, you should check the ca. Secretary of State website ( http://www.sos.ca.gov/business/be/ ) which will tell you if it is a corporation and who the "Agent for Service of Process" is.
As to the government entity, generally speaking you have to file a claim, which has to be rejected, before you can file the lawsuit. Suits against government entity are very technical and you should probably contact an attorney. I hope this helps.