Many thanks for your post and welcome to the forums! I'm really sorry you're having issues with your landline at the moment.
Thanks for confirming the checks you've already carried out - this helps narrow things down. I've been able to locate your account using your forums details and have been unable to connect with the phone to run deeper checks. There is also no area outage that could be impacting things.
I'd like to get a tech visit booked into you so we can look into this and get it fixed. I'll just need to confirm a couple of details, please look out for the purple envelope at the top of the page.