Gigaclear and a 'Blocked Duct'

Can anyone shed light on what a "Blocked Duct" is?
I had my installation done on the 15th Dec but I am still not connected. The installation team said that an enginner had forgotten/messed-up the connection at the green box and they had no access. Support says it is a blocked duct and a team needs to visit to resolve.
I have cable into the house and I watched them lift the manhole cover and connect me to the Gigaclear trunk, so where is the blockage?
Really not happy that 4 weeks later I am still not connected.

Ordinarily, a blocked duct is just that, a duct exists to get your fibre from A to B, but is blocked/silted up, and will require jetting out, or civils to dig on the blockage.

So as I watched them connect my fibre cable at the house end and to the main cable in the local duct Gigaclear are talking out of their .... again. Strange how houses further up the road are getting installations and connected.