By default the Yealink YMCS portal will be allowed to capture screenshots or PCAPs from the devices by prompting the user to allow it.
If you want to get a screenshot or a PCAP from a device without prompting the user, you will need to apply the following configuration parameter to the phone:
To allow screenshots without prompting the user to allow it:
static.remote_control.1.allow="1"
To allow for PCAPs to be collected without prompting the user to allow it:
static.remote_control.3.allow="1"