Princh strives to make it possible to print from as many apps as possible. However, sometimes a particular app does not support sending a document to Princh or other 3rd party applications.
If are you trying to print from an app that is not supported, check if the file can be opened in another app instead and print from there, or try printing from a computer if available. Please also let us know which app caused the problem so that we can potentially fix the issue.