As far as why there is now a problem, it’s impossible to know , there may be a complete break in the fibre , there may be a high loss , or your ONT may have developed a fault , it’s likely that the problem is the splitter forward towards your ONT , so only you affected , but it’s possible the problem is splitter back towards the headend and affecting all the members of the PON , so unto 30 customers , but it’s not likely that OR have 100% take up , so many fewer if the PON is out of order .
With lots of companies allowed access to Openreach physical infrastructure, like ducts , joint boxes and poles , it’s possible someone has damaged OR cables while working on /installing a competitor company cables or equipment , there are quite a number of possibilities, but it’s nothing more than speculation until OR visit and locate the issue , even when fixed , although the defect can be identified the reason for it may never be known
