Answer
One of the likely reasons this could happen is if your PrizmDoc Server is not licensed properly or if you are running in the Evaluation mode. In such cases, there are restrictions in place.
Among those restrictions is an artificial delay of 10 seconds imposed before viewing or conversion operations begin. A dialog window normally indicates this in the Viewer interface, but if you are just making API calls to the server, it will not be apparent.
A valid product license is required to eliminate these restrictions, which can be done as follows: https://help.accusoft.com/PrizmDoc/latest/HTML/prizmdoc-server-docker.html#2-configure-your-license .