There have been issues stemming from the simultaneous streaming limit while using the Axis M7001 Encoder.
I have found in the Axis User manual on Page 9 (http://www.axis.com/files/manuals/um_m7001_43683_en_1107.pdf):
"The AXIS M7001 Video Encoder supports simultaneous streaming of one H.264 stream and one Motion JPEG stream,
individually configured with different resolutions, bit rates, compression levels etc. The error message “503 service
unavailable” is shown if the maximum number of simultaneous streams is exceeded, for example if a user requests a Motion
JPEG stream while another user is accessing Motion JPEG video with a different stream configuration."
There are two ways I have found to work around this issue.
1. Use a browser that supports Silverlight or force Silverlight throughout ESM (Please see knowledgebase article for instructions: https://ipconfigure.zendesk.com/entries/28206506-Forcing-Silverlight-on-Internet-Explorer
2. Switch live view to a different Codec than recording. Unfortunately, you may still run into some issues when you try pull live view in matrix in different layouts and/or pop out (right-click>>View) the camera in live view (different resolutions) because it will exceed it limitations for the encoder.
However, we may be able work around the encoder issue by taking the other resolutions out of the databases so ESM will only be able to stream one resolution throughout. Please contact our support team if you want to try this possible solution.