A total loss of service is defined in point 16 below
https://www.virginmedia.com/legal/fibre-optic-services-terms-conditions/automatic-compensation
The compensation for a TLS only applies to broadband and/or landline phone (not TV).
I had understood the 'online' reporting reference to mean using the service status test within 'My Virgin Media' which may report a fault. I had also understood the automated service status number 0800 561 0061 would log a fault if it reported a TLS was present. I could be wrong on this though.
The last drop down at the bottom here
https://www.virginmedia.com/help/billing-and-payments/automatic-compensation
states that reporting on forums will not count.
You may not have access to any of the above in a TLS. Your best bet is to phone in any TLS fault IMHO for the purposes of compensation (using a mobile or another line).
Once you have done that, keep detailed notes of VM's responses and time taken to repair. VM's payment of automatic compensation is sometimes not quite so 'automatic' when reported in topics on here.
The two working day wait means that often customers will be due no compensation even with an outage of a few days (such as over a bank holiday weekend).