Have you just moved into the property so don’t know who ( if anyone ) was supplying the previous broadband service , ( it may not have been Openreach ) or have you lived in the property for a while but were using a non Openreach based supplier , in these cases , there could be various reasons for service not simply starting to work on the date you were given , the simplest reason may be that you may not be connected to the correct Openreach socket ( if the address has more than one Openreach socket ) , or the ‘line’ from the address to cabinet ( assuming you are taking FTTC ) has in the period between now and when it was last in service ( which may have been years ago ) is no longer intact .
As stated lines that are started in these circumstances ( a gap of many months or even years since the line last delivered service ) should be dealt with as early life failure, if they don’t simply start back up .
https://www.bt.com/help/broadband/fix-a-problem/broadband-and-wi-fi/what-do-the-lights-on-my-bt-hub-...
It is only really if you had service working service already from one Openreach provider and migrating to BT that there is overwhelming expectation that it’s not going to be problematic , so what’s your ‘story’ , is this your first service with an Openreach based product at this address , or there has been a big gap between now and the last time you had Openreach service , or the line was working up until very recently for you with another provider and it’s only the change to BT that has affected this .
