Is this flat a new build , you are the first occupant and the ONT was already in place when you moved in ?, if so , the chances are developers fitted the ONT on Openreach’s behalf ( a job OR pay them to do ) but the developers can’t connect ( splice ) the fibre infrastructure , when the flat is ‘called off’ as ready for occupation the developer should let their OR contact know, and the OR contact ( FBC /new site rep ) arranges for an OR engineer to splice the connection through and authenticate the ONT with the headend.
If the developer has fitted the kit , and allowed occupation of the flat but either hasn’t advised OR of that fact , or the developer built these properties in a different order to how they advised OR initially the site was to progress ( for example the developer said to OR the first phase was the ‘east’ of the site and would progress ‘west’ , so OR program work to start at the east entrance to the site ,) the developer then builds something at the ‘west’ side , when the OR network is still being built east to west , then the occupants of that building have to wait for the network to reach them……chances are your developer hasn’t kept OR informed, and unlike water and electricity, developers can ‘sell’ buildings without ‘broadband’ they cannot sell buildings without water or electricity.
Obviously, if none of this applies to you, then it cannot be your issue , but if your address was retro fitted with FTTP on top of the copper pair network, then if the ONT was never authenticated ( the flashing PON signifies it isn’t ) then the OR installer shouldn’t have booked the install off as ‘done’
