Hi there @jp004a7672
Welcome back to our Co9mmunity - sorry to understand that you've had some issues with your landline since having a power cut. I have located your account from here to take a closer look at your line and can see that you have our standard landline service via a wall socket.
There are currently no known area issues showing at the time of checking - you advise you have done all the usual things; can you advise what they are?
Have you tried a new handset at all to see if that helps? Please do try a non-cordless handset if you can.
Also, if you are getting an engaged tone when you dial your number, this can sometimes suggest the line is blocked and this can occasionally be resolved without a technician visit. Please unplug all handsets in any and all sockets in your home for at least 20/30 minutes. This should force the line to unblock. Then place one corded handset into the main master socket and see if you now have a dial tone.
Keep us posted and we can refresh and check again this end
Cheers