Thanks for the suggestion Mimesis. Reading the comment about using 'a cheap switch', I looked at the switch I was temporarily using to connect the laptop and Meridian devices.
It was a Netgear GS105E. It was a cheap switch, but looking at the Netgear webpage, a support app can be download to update it's firmware.

I did this and noticed that a second GS105E also appeared. It is a switch installed in the back of the TV cabinet in the living room.

After updating the firmware on both switches, I looked at the other available options in the app and found a Multicast page for IGMP Snooping Configuration.
It was enabled, so I disabled 'IGMP Snooping Status' and 'Block Unknown MultiCast Address'. I repeated this for the second switch.

This solved the problem and I was able to update both Meridian devices.