What is the make and model number of the DVR player?
What app are you trying to set up?
If the DVR app is showing as "buffering" and "no response" then a firewall may be preventing the DVR from communicating with the smartphone app.
You will need to open the specified port for mobile devices; this should be indicated in the documents supplied with the DVR system.
Hi there and welcome
Can you download and use the app IP Cam Viewer.
Tell me if that app connects to your DVR
Let me know the results please.