Does your connection still have a cable terminator cap fitted (the 'hexagonal nuts' in your description)? As per these
If so, these are required on unused cable connections but are removed in order to make a new connection to equipment.
Post up some clear photos of your wall box/connections which will help identify what you have in place and what you should connect to.
You can try push fitting the VM lead provided by VM onto either one of the two outputs of the splitter. See if you can get connected.
If you are only connecting one piece of equipment, you don't need the splitter (which is marked with an insertion loss of 3.6 dB and should ideally have a terminator cap on the unused connection).
If the white cable is the incoming VM cable you could remove the splitter by unscrewing it from the cable but you would need to get an F-connector coupler like this though
to be able to join the two plugs together.
If you want to avoid the trailing lead altogether, would need a VM tech to fit a wall box for you which might be most suitable for long term use.
Try connecting to the splitter first and see if you can connect at all.
I have the same problem.... same type of connection with the old splitter.
Everything is plugged in but the modem box keeps flashing red
You would do best to stick to your own/original topic
multi-posting just causes confusion when the same question is asked in different places. It normally takes the VM forum team two or three days to reply to each person's topic.