Sometimes if you have enabled H265 on your cameras you may receive the following message when trying to view live video:
This camera has enabled H.265 streams that this browser can not play. Ensure you have installed an HEVC codec.
The first thing to verify is that your browser has Hardware Accelleration enabled. Go to the settings for your browser and ensure it is turned on.
This can be found in the browser settings. Below are the examples from Chrome and Firefox. We have found that sometimes third party applications can turn this setting off if it suits them. So always double check this if you are having trouble.
HEVC is another name for H.265. Due to its nature, H265 requires proper decoding. Some browsers and operating systems come with this codec by default. We often suggest trying Chrome if you have not started there. If none of the local browsers work, you will need to install the HEVC Codec independently. For MacOS you simply need to be on High Sierra (2017) or higher.
For windows simply browse to the Microsoft Store and search HEVC. 
Please note this is a per computer option. You may need to install HEVC on more than one computer.